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SHR<br />
-A-<strong>379</strong><br />
The SUPERPAVE Mix Design System<br />
Manual of Specifications,<br />
Test Methods, and Practices<br />
Edited by E.T. Harrigan, R.B. Leahy and J.S. Youtcheff<br />
Strategic Highway Research Program<br />
With contributions<br />
by the staffs of:<br />
<strong>SHRP</strong> contract A-001, University of Texas at Austin<br />
The Asphalt Institute<br />
Heritage Research Group<br />
<strong>SHRP</strong> contract A-002A, Western Research Institute<br />
Penn State University<br />
<strong>SHRP</strong> contract A-003A, University of California at Berkeley<br />
Oregon State University<br />
ARE Inc.<br />
<strong>SHRP</strong> contract A-003B, National<br />
Center for Asphalt Technology,<br />
Auburn University<br />
<strong>SHRP</strong> contract P-005, Brent Rauhut Engineering,<br />
Inc.<br />
Strategic Highway Research Program<br />
National Research Council<br />
Washington, DC 1994
<strong>SHRP</strong>-A-<strong>379</strong><br />
ISBN 0-309-05764-7<br />
Contract A-001, A-002A, A-003A, A-003B, P-005<br />
Product Nos. 1012<br />
Program Manager: Edward T. Harrigan<br />
Project Managers: Rita B. Leahy<br />
Jack S. Youtcheff<br />
Program Area Secretary: Juliet Narsiah<br />
Copyeditor: Katharyn L. Bine<br />
Production Editor: Lynn E. Stanton<br />
March 1994<br />
key words:<br />
aggregate<br />
asphalt binder<br />
asphalt cement<br />
asphalt modifier<br />
bending beam rheometer<br />
direct tension<br />
dynamic shear rheometer<br />
environmental conditioning system<br />
gyratory compaction<br />
hot mix asphalt<br />
indirect tensile test device<br />
net adsorption<br />
performance grade<br />
pressurized aging vessel<br />
rolling wheel compaction<br />
shear test device<br />
SUPERPAVE ®<br />
Strategic Highway Research Program<br />
National Academy of Sciences<br />
2101 Constitution Avenue N.W.<br />
Washington, DC 20418<br />
(202) 334-3774<br />
The publication of this report does not necessarily indicate approval or endorsement of the findings, opinions,<br />
conclusions, or recommendations either inferred or specifically expressed herein by the National Academy of<br />
Sciences, the United States Government, or the American Association of State Highway and Transportation<br />
Officials or its member states.<br />
©1994 National Academy of Sciences<br />
1.5M/NAP/0394
Acknowledgments<br />
The research described herein was supported by the Strategic Highway Research Program<br />
(<strong>SHRP</strong>). <strong>SHRP</strong> is a unit of the National Research Council that was authorized by section<br />
128 of the Surface Transportation and Uniform Relocation Assistance Act of 1987.<br />
°°°<br />
111
Contents<br />
Acknowledgments ................................................. iii<br />
Abstract ........................................................ vii<br />
Introduction ...................................................... ix<br />
Test Methods for Asphalt<br />
Binders<br />
MP1 Performance-Graded Asphalt Binder ...................... 1<br />
TP1 Determining the Flexural Creep Stiffness of Asphalt Binder<br />
Using the Bending Beam Rheometer ...................... 7<br />
TP5 Determining the Rheological Properties of Asphalt Binder<br />
Using a Dynamic Shear Rheometer ...................... 29<br />
TP3 Determining the Fracture Properties<br />
of Asphalt Binder in Direct Tension ..................... 43<br />
PP1 Accelerated Aging of Asphalt Binder<br />
Using a Pressurized Aging Vessel ....................... 61<br />
B-006 Extraction and Recovery of Asphalt Cement<br />
for Rheological Testing .............................. 71<br />
Test Methods<br />
for Hot Mix Asphalt<br />
M-001 The Measurement of Initial Asphalt Adsorption<br />
and Desorption in the Presence of Moisture ................ 87<br />
M-002 Preparation of Compacted Specimens of Modified<br />
and Unmodified Hot Mix Asphalt by Means<br />
of the <strong>SHRP</strong> Gyratory Compactor ....................... 95<br />
V
M-003 Determining the Shear and Stiffness Behavior<br />
of Modified and Unmodified Hot Mix Asphalt<br />
with the SUPERPAVE ® Shear Test Drive ................ 103<br />
M-005 Determining the Creep Compliance and Strength<br />
of Modified and Unmodified Hot Mix Asphalt<br />
Using Indirect Tensile Loading Techniques ............... 121<br />
M-006 Determining Moisture Sensitivity Characteristics<br />
of Compacted Bituminous Mixtures Subjected<br />
to Hot and Cold Climate Conditions .................... 137<br />
M-007 Short- and Long-Term Aging of Bituminous Mixes .......... 159<br />
M-008 Preparation of Test Specimens of Bituminous Mixtures<br />
by Means of Rolling Wheel Compaction ................. 165<br />
M-009 Determining the Fatigue Life of Compacted Bituminous<br />
Mixtures Subjected to Repeated Flexural Bending ........... 177<br />
M-010 Determining the Fracture Strength and Temperature<br />
of Modified and Unmodified Hot Mix Asphalt<br />
Subjected to Cold Temperatures ....................... 191<br />
Practices<br />
and Protocols<br />
PP5 The Laboratory Evaluation of Modified Asphalt Systems ...... 203<br />
PP6 Grading or Verifying the Performance Grade<br />
of an Asphalt Binder ............................... 225<br />
P-004 Volumetric Analysis of Compacted Hot Mix Asphalt ......... 233<br />
P-005 Measurement of the Permanent Deformation<br />
and Fatigue Cracking Characteristics<br />
of Modified and Unmodified Hot Mix Asphalt ............. 239<br />
vi
Abstract<br />
The final product of the <strong>SHRP</strong> Asphalt Research Program is the SUPERPAVE ® mix design<br />
system for new construction and overlays. This system employs a series of new<br />
performance-based specifications, test methods and practices for material selection,<br />
accelerated performance testing, and mix design. This report documents these new<br />
specifications and procedures in a format suitable for eventual AASHTO standardization.<br />
vii
Introduction<br />
This volume of the Final Report of the <strong>SHRP</strong> Asphalt Research Program presents the<br />
specifications, test methods and practices that form the SUPERPAVE ® mix design system.<br />
These specifications, test methods and practices were developed in <strong>SHRP</strong> contracts A-001,<br />
A-002A, A-003A and A-003B.<br />
The <strong>SHRP</strong>-developed specifications, test methods and practices contained in this volume are<br />
listed in table 1. Table 2 provides a supplementary list of AASHTO, ASTM, and other test<br />
methods used in the SUPERPAVE* system; the text of these methods and practices are not<br />
included in this volume.<br />
At the end of the <strong>SHRP</strong> asphalt research program, the methods and practices in table 1 were<br />
provided to the AASHTO Subcommittee on Materials for review and action towards their<br />
ultimate adoption as AASHTO standard methods of test. These methods and practices, while<br />
judged to be substantially accurate, will undergo further changes and revisions as AASHTO<br />
evaluation and adoption proceeds.<br />
ix
Table 1. <strong>SHRP</strong> Test Methods and Practices 1<br />
<strong>SHRP</strong> AASm_ Test Method<br />
Test Provisional<br />
Number Number<br />
none MP1 Performance-Graded Asphalt Binder<br />
B-002 TP1 Test Method for Determining the Flexural Creep Stiffness of an Asphalt Binder<br />
Using the Bending Beam Rheometer<br />
B-003 TP5 Test Method for Determining the Rheological Properties of an Asphalt Binder<br />
Using a Dynamic Shear Rheometer<br />
B-004 TP3 Test Method for Determining the Fracture Properties of an Asphalt Binder in<br />
Direct Tension<br />
B-005 PP1 Practice for Accelerated Aging of an Asphalt Binder Using a Pressurized Aging<br />
Vessel<br />
B-006 none Extraction and Recovery of Asphalt Cement for Rheological Testing<br />
M-001 none The Measurement of Initial Asphalt Adsorption and Desorption in the Presence<br />
of Moisture (Net Adsorption Test)<br />
M-002 none Preparation of Compacted Specimens of Modified and Unmodified Hot Mix<br />
Asphalt by Means of the <strong>SHRP</strong> Gyratory Compactor<br />
M-003 none Determining the Shear and Stiffness Behavior of Modified and Unmodified Hot<br />
Mix Asphalt with the SUPERPAVE ® Shear Test Device<br />
M-005 none Determining the Creep Compliance and Strength of Modified and Unmodified<br />
Hot Mix Asphalt Using Indirect Tensile Loading Techniques<br />
M-006 none Determining Moisture Sensitivity Characteristics of Compacted Bituminous<br />
Mixtures Subjected to Hot and Cold Climate Conditions<br />
M-007 none Short- and Long-Term Aging of Bituminous Mixes<br />
M-008 none Preparation of Test Specimens of Bituminous Mixtures by Means of Rolling<br />
Wheel Compaction<br />
M-009 none Determining the Fatigue Life of Compacted Bituminous Mixtures Subjected to<br />
Repeated Flexural Bending<br />
M-010 none Determining the Fracture Strength and Temperature of Modified and Unmodified<br />
Hot Mix Asphalt Subjected to Cold Temperatures<br />
P-001 PP5 Guide for the Laboratory Evaluation of Modified Asphalt Systems<br />
P-002 PP6 Guide for Grading or Verifying the Performance Grade of an Asphalt Binder<br />
P-004 none Volumetric Analysis of Compacted Hot Mix Asphalt<br />
P-005 none Measurement of the Permanent Deformation and Fatigue Cracking<br />
Characteristics of Modified and Unmodified Hot Mix Asphalt<br />
IB = Test Method for Asphalt Binders; M = Test Method for Hot Mix Asphalt; and PP = Practice or<br />
Protocol.<br />
X
Table 2. AASHTO<br />
and Other Test Methods<br />
Test Number<br />
Test Method<br />
AASHTO T27 Sieve Analysis of Fine and Coarse Aggregates<br />
AASHTO T37 Sieve Analysis of Mineral Filler<br />
AASHTO T44 Solubility of Bituminous Materials in Organic Solvents<br />
AASHTO T48 Flash and Fire Points by Cleveland Open Cup<br />
AASHTO T84 Specific Gravity and Absorption of Fine Aggregate<br />
AASHTO T85 Specific Gravity and Absorption of Coarse Aggregate<br />
AASHTO T96 Resistance to Abrasion of Small Size Coarse Aggregate by Use of the<br />
Los Angeles Machine<br />
AASHTO T100 Specific Gravity of Soils _<br />
AASHTO T104 Soundness of Aggregate by Use of Sodium Sulfate or Magnesium<br />
Sulfate<br />
AASHTO T112 Clay Lumps and Friable Particles in Aggregate<br />
AASHTO T164 Quantitative Extraction of Bitumen from Bituminous Paving Mixtures<br />
AASHTO T166 Bulk Specific Gravity of Compacted Bituminous Mixtures<br />
AASHTO T170 Recovery of Asphalt from Solution by Abson Method<br />
AASHTO T176 Plastic Fines in Graded Aggregates and Soils by Use of the Sand<br />
Equivalent Test<br />
AASHTO T201 Kinematic Viscosity of Asphalts<br />
AASHTO T209 Maximum Specific Gravity of Bituminous Paving Mixtures<br />
AASHTO T228 Specific Gravity of Semi-Solid Bituminous Materials<br />
AASHTO T240 Effect of Heat and Air on a Moving Film of Asphalt (Rolling Thin<br />
Film Oven Test)<br />
AASHTO T283 Resistance of Compacted Bituminous Mixture to Moisture-Induced<br />
Damage<br />
ASTM D4402 Measurement of Asphalt Viscosity Using a Rotational Viscometer<br />
ASTM D4791 Flat or Elongated Particles in Coarse Aggregate<br />
National Aggregates Association Fine Aggregate Angularity<br />
Test Method A<br />
Pennsylvania Test Method No. Determining the Percentage of Crushed Fragments in Gravel<br />
621 (April 1987)<br />
1Used to measure the specific gravity of mineral fillers.<br />
xi
Standard Method of Test for<br />
Performance-Graded Asphalt Binder<br />
AASHTO Designation: MPll<br />
1. SCOPE<br />
1.1 This specification covers asphalt binders graded by performance. Grading<br />
designations are related to average 7-day maximum pavement design temperatures and<br />
minimum pavement design temperatures.<br />
NOTE1.--For asphaltcementsgradedby penetrationat 25"C, seeM20. For asphaltcementsgradedby<br />
viscosityat 60°C, seeM226.<br />
NoTE2.--GuidePP5providesinformationonthe evaluationof modifiedasphaltbinders.<br />
NOTE3.--GuidePP6providesinformationfordeterminingthe performancegradeof an asphaltbinder.<br />
1.2 The values stated in SI units are to regarded as the standard.<br />
1.3 This standard may involve hazardous materials, operations and equipment. This<br />
standard does not purport to address all of the safety problems associated with its use. It is<br />
the responsibility of the user of this standard to establish appropriate safety and health<br />
practices and determine the applicability of regulatory limitations prior to use.<br />
2. REFERENCED DOCUMENTS<br />
2.1 AASHTO Standards:<br />
PP5<br />
PP6<br />
Guide for the Laboratory Evaluation of Modified Asphalt Systems<br />
Guide for Grading or Verifying the Performance Grade of an Asphalt<br />
Binder<br />
PPX Selection of Asphalt Binders (being developed)<br />
M20 Specification for Penetration-Graded Asphalt Cement<br />
M226 Specification for Viscosity-Graded Asphalt Cement<br />
PP1 Practice for Accelerated Aging of an Asphalt Binder Using a Pressurized<br />
Aging Vessel<br />
T40 Practice for Sampling Bituminous Materials<br />
T44 Solubility of Bituminous Materials in Organic Solvents<br />
1This standardis basedon <strong>SHRP</strong>Product1001.
T48 Method of Test for Flash and Fire Points by Cleveland Open Cup<br />
T55 Method of Test for Water in Petroleum Products and Bituminous Materials<br />
by Distillation<br />
T179 Test Method for Effect of Heat and Air on Asphalt Materials (Thin Film<br />
Oven Test)<br />
T201 Kinematic Viscosity of Asphalts<br />
T202 Viscosity of Asphalts by Vacuum Capillary Viscometer<br />
T240 Test Method for Effect of Heat and Air on a Moving Film of Asphalt<br />
(Rolling Thin Film Oven Test)<br />
TP1 Test Method for Determining the Flexural Creep Stiffness of an Asphalt<br />
Binder Using the Bending Beam Rheometer<br />
TP3 Test Method for Determining the Fracture Properties of an Asphalt Binder<br />
in Direct Tension<br />
TP5 Test Method for Determining the Rheological Properties of Asphalt Binder<br />
Using a Dynamic Shear Rheometer<br />
2.2 ASTM Standards:<br />
D8 Definitions of Terms Relating to Materials for Roads and Pavements<br />
D4402 Method for Viscosity Determinations of Unfilled Asphalt Using the<br />
Brookfield Thermosel Apparatus<br />
2.3 <strong>SHRP</strong> Documents:<br />
P00X SUPERPAVE Software (being developed)<br />
3. TERMINOLOGY<br />
3.1 Definitions:<br />
3.1.1 Definitions for many terms common to asphalt cement are found in ASTM D8.<br />
3.1.2 asphalt binder, n--an asphalt-based cement that is produced from petroleum<br />
residue either with or without the addition of non-particulate organic modifiers.<br />
4. ORDERING INFORMATION--When ordering under this specification, include in the<br />
purchase order the performance grade of asphalt binder required from table 1 (e.g.,<br />
PG 52-16 or PG 64-34).<br />
4.1 Asphalt binder grades may be selected by following the procedures described in<br />
provisional practice PPX, Selection of Asphalt Binders.<br />
2
5. MATERIALS AND MANUFACTURE<br />
5.1 Asphalt cement shall be prepared by the refining of crude petroleum by suitable<br />
methods, with or without the addition of modifiers.<br />
5.2 Modifiers may be any organic material of suitable manufacture, used in virgin or<br />
recycled condition, and that is dissolved, dispersed or reacted in asphalt cement to enhance<br />
its performance.<br />
5.3 The base asphalt binder shall be homogeneous, free from water and deleterious<br />
materials, and shall not foam when heated to 175°C.<br />
5.4 The base asphalt binder shall be at least 99.0% soluble in trichloroethylene as<br />
determined by AASHTO T44.<br />
5.5 The bending beam rheometer test, TP1, the direct tension test, TP3, and the<br />
dynamic shear rheometer test, TP5, are not suitable for asphalt binders in which fibers or<br />
other discrete particles are larger than 250 #m in size.<br />
5.6 The grades of asphalt binder shall conform to the requirements given in table 1.<br />
6. SAMPLING<br />
The material shall be sampled in accordance with T40.<br />
7. TEST METHODS<br />
The properties outlined in 5.3, 5.4 and 5.6 shall be determined in accordance with T44, T48,<br />
T55, T179, T240, PP1, TP1, TP3, TP5, and ASTM D4402.<br />
8. INSPECTION AND CERTIFICATION<br />
Inspection and certification of the material shall be agreed upon between the purchaser and<br />
the seller. Specific requirements shall be made part of the purchase contract.<br />
9. REJECTION AND REHEARING<br />
If the results of any test do not conform to the requirements of this specification, retesting to<br />
determine conformity is performed as indicated in the purchase order or as otherwise agreed<br />
upon between the purchaser and the seller.
10. KEY WORDS<br />
Asphalt binder, asphalt cement, direct tension, flash point, modifier, performance<br />
specifications, pressure aging, rheology.<br />
4
Table 1. Performance-Graded Asphalt Binder Specification<br />
PERFORMANCE<br />
PG 46- PG 52- PG 58- PG 64-<br />
GRADr 34140146 1011612212S134140146 16122[28[34[40 10116[22128[34140<br />
Average 7-day Maximum<br />
Pavement Design < 46 < 52 < 58 < 64<br />
Temperature,<br />
°C a<br />
IIl[Iq Illl dllil<br />
Temperature, °ca > -34 > -40 >-46 >-10 > -16 >-22 >-28 > -34 > - >-46 > -16 > -22 >-28 > -34 >-40 >-1 >-16 >-22 > -28 >-34 >-40<br />
Minimum Pavement Design II<br />
ORIGINAL<br />
BINDER<br />
Flash Point Temp, T48:<br />
Minimum °C 230<br />
Viscosity, ASTM D4402b:<br />
Maximum, 3 Pa.s, 135<br />
Test Temp, °C<br />
Dynamic Shear, TP5C:<br />
G*/sin_, Minimum, 1.00 kPa 46 52 58 64<br />
Test Temp @ 10 rad/s, °C<br />
ROLLING THIN FILM OVEN (T240) OR THIN FILM OVEN RESIDUE (T179)<br />
Mass Loss, Maximum, percent 1.00<br />
Dynamic Shear, TP5:<br />
G*/sin_, Minimum, 2.20 kPa 46 52 58 64<br />
Test Temp @ 10 rad/s, °C<br />
PRESSURE AGING VESSEL (PAV) RESIDUE (PP1)<br />
PAV Aging Temperature, °C a 90 90 100 100<br />
Dynamic Shear, TPS:<br />
G*sin_, Maximum, 5000 kPa<br />
Test Temp @ 10 rad/s, °C 10 7 4 25 22 19 16 13 10 7 25 22 19 16 13 31 28 25 22 19 16<br />
Physical Hardening _ Report<br />
Creep Stiffness,<br />
TPI: r<br />
S, Maximum, 300 MPa,<br />
m - value, Minimum, 0.300 -24 -30 -36 0 -6 -12 -18 -24 -30 -36 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 -30<br />
Test Temp @ 60s, °C<br />
Direct Tension, TP3: r<br />
Failure Strain, Minimum, 1.0% -24 -30 -36 0 -6 -12 -18 -24 -30 -36 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 -30<br />
Test Temp @ 1.0 ram/rain, °C<br />
a Pavement temperatures may be estimated from air temperaturesusing an algorithm contained in the SUPERPAVE software<br />
program; provided by the specifying agency; or found by following the procedures as outlined in PPX.<br />
b This requirement may be waived at the discretion of the specifying agency if the supplier warrants that the asphalt binder can<br />
be adequately pumped and mixed at temperatures that meet all applicable safety standards.<br />
° For quality control of unmodified asphalt cement production, measurement of the viscosity of the original asphalt cement may<br />
be substituted for dynamic shear measurements of G*/sin6 at test temperatures where the asphalt is a Newtunian fluid. Any<br />
suitable standard means of viscosity measurement may be used, including capillary or rotational viscometry (AASHTO T201 or<br />
T202).<br />
d The PAV aging temperature is based on simulated climatic conditions and is one of three temperatures: 900C, 100*C or<br />
110*C. The PAV aging temperature is 100*C for PG 58- and above, except for paving materials to be used in desert climates,<br />
where it is ll0*C.<br />
c Physical Hardening--TP1 is performed on a set of asphalt beams according to section 13.1, except the conditioning time is<br />
extended to 24 hrs + 10 minutes at 10*C above the minimum performance temperature. The 24-hour stiffness and m-value are<br />
reported for information purposes only.<br />
f If the creep stiffness is below 300 MPa, the direct tension test is not required. If the creep stiffness is between 300 and 600<br />
MPa, the direct tension failure strain requirement can be used in lieu of the creep stiffness requirement. The m-value<br />
requirement must be satisfied in both cases.
Table 1. Performance-Graded Asphalt Binder Specification (Continued)<br />
PG 70- PG 76- PG 82-<br />
PERFORMANCE GRADE 10116[22128[34 [ 40 10 I 161 22 I 28 [ 34 10 I 16 [ 22 I 28 ] 34<br />
Average 7-day Maximum<br />
Pavement Design < 70 < 76 < 82<br />
Temperature, °Cb<br />
TMienmip_Pa,VecentDesign<br />
>_>1_>_>_l>_>o>o1>01>_1>_1>_>o1>o1>_1>_I>_<br />
ORIGINAL<br />
BINDER<br />
Flash Point Temp, T48: 230<br />
Minimum °C<br />
Viscosity, ASTM D4402._<br />
Maximum, 3 Pa.s, 135<br />
Test Temp, °C<br />
Dynamic Shear, TPS:c<br />
G*/sin6, Minimum, 1.00 kPa 70 76 82<br />
Test Temp @ 10 tad/s, °C<br />
ROLLING THIN FILM OVEN (T240) OR THIN FILM OVEN (T179) RESIDUE<br />
Mass Loss, Maximum, percent 1.00<br />
Dynamic Shear, TPS:<br />
G*/stn_, Minimum, 2.20 kPa 70 76 82<br />
Test Temp @ 10 rad/s, °C<br />
PRESSURE AGING VESSEL (PAV) RESIDUE (PP1)<br />
PAV Aging Temperature, °Cd 100(110) 100(110) 100(110)<br />
Dynamic Shear, TPS:<br />
G*sin_, Maximum, 5000 kPa 34 31 28 25 22 19 37 34 31 28 25 40 37 34 31 28<br />
Test Temp @ 10 rad/s, °C<br />
Physical Hardening*<br />
Creep Stiffness, TPI: f<br />
S, Maximum, 300.0 MPa,<br />
m - value, Minimum, 0.300 0 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 0 -6 -12 -18 -24<br />
Test Temp @ 60s, °C<br />
Direct Tension, TP3:f<br />
Failure Strain, Minimum, 1.0% 0 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 0 -6 -12 -18 -24<br />
Test Temp @ 1.0 mm/min, °C<br />
Report<br />
6
Standard Method of Test for<br />
Determining the Flexural Creep Stiffness<br />
of Asphalt Binder Using the Bending Beam<br />
Rheometer<br />
AASHTO Designation: TPll<br />
1. SCOPE<br />
1.1 This test method covers the determination of the flexural creep stiffness or<br />
compliance of asphalt binders by means of a bending beam rheometer. It is applicable to<br />
material having flexural creep stiffness values from 30 MPa to 1 GPa (creep compliance<br />
values in the range of 300 mPa -1 to 1 nPa-X). It can be used with unaged material or with<br />
material aged using T240, T179, or PP1. The test apparatus is designed for testing within the<br />
temperature range of -40 to 25°C.<br />
1.2 Test results are not valid for beams of asphalt binder that deflect more than<br />
4 mm when tested in accordance with this method.<br />
1.3 The values stated in SI units are to be regarded as the standard.<br />
1.4 This standard may involve hazardous materials, operations, and equipment. This<br />
standard does not purport to address all of the safety problems associated with its use. It is<br />
the responsibility of the user of this procedure to establish appropriate safety and health<br />
practices and to determine the applicability of regulatory limitations prior to use.<br />
2. REFERENCE DOCUMENTS<br />
2.1 AASHTO Standards:<br />
MP1 Standard Method of Test for Performance-Graded Asphalt Binder<br />
PP1 Practice for Accelerated Aging of an Asphalt Binder Using a Pressurized<br />
Aging Vessel<br />
T40 Practice for Sampling Bituminous Materials<br />
T179 Test Method for Effect of Heat and Air on Asphalt Materials (Thin Film<br />
Oven Test)<br />
T240 Test Method for Effect of Heat and Air on Rolling Film of Asphalt (Rolling<br />
Thin Film Oven Test)<br />
1This standardis basedon <strong>SHRP</strong>Product 1002.<br />
7
2.2 ASTM Standards:<br />
C802 Conducting an Interlaboratory Test Program to Determine the Precision of Test<br />
Methods for Construction Materials<br />
E1 Specification for ASTM Thermometers<br />
E77 Standard Test Method for Inspection and Verification of Liquid-in-Glass<br />
Thermometers<br />
2.3 DIN Standards:<br />
43760<br />
3. TERMINOLOGY<br />
3.1 Definitions:<br />
3.1.1 asphalt binder, n--an asphalt-based cement that is produced from petroleum<br />
residue either with or without the addition of non-particulate organic modifiers.<br />
3.1.2 physical hardening, n--a time-dependent stiffening of asphalt binder that results<br />
from time-delayed increase in stiffness when the asphalt binder is stored at low temperatures.<br />
3.2 Descriptions of Terms Specific to this Standard:<br />
3.2.1 flexural creep, n--a material characteristic determined by a test in which a<br />
simply-supported beam is loaded with a constant load at its midpoint and the deflection of the<br />
beam is measured with respect to loading time.<br />
3.2.2 flexural creep stiffness, S(t)--ratio obtained by dividing the maximum bending<br />
stress in the beam by the maximum bending strain.<br />
3.2.3 flexural creep compliance, D(t)--ratio obtained by dividing the maximum<br />
bending strain in the beam by the maximum bending stress. D(t) is the inverse of S(t). S(t)<br />
has been used historically in asphalt technology while D(t) is commonly used in studies of<br />
viscoelasticity.<br />
logarithm<br />
3.2.4 m--absolute value of the slope of the logarithm of the stiffness curve versus the<br />
of time.<br />
3.2.5 preload, n--load required to maintain positive contact between the beam and<br />
the loading shaft; 30 + 5 raN.<br />
3.2.6 initial seating load, n--load of 1-s duration required to seat the beam; 980 5:<br />
50 mN.<br />
3.2.7 test load, n--load of 240-s duration required to determine the stiffness of the<br />
material being tested; 980 5:50 mN.<br />
8
4. SUMMARY OF TEST METHOD<br />
4.1 The bending beam rheometer measures the midpoint deflection of a simplysupported<br />
prismatic beam of asphalt binder that is subjected to a constant load applied to the<br />
midpoint of the beam. The device operates only in the loading mode. Recovery<br />
measurements are not obtained.<br />
4.2 A test beam is placed in the controlled temperature fluid bath and loaded with a<br />
constant load for 240 seconds. The test load (980 :t: 50 mN) and the midpoint deflection of<br />
the beam are monitored versus time using a computerized data acquisition system.<br />
4.3 The maximum bending stress at the midpoint of the beam is calculated from the<br />
dimensions of the beam, the span length, and the load applied to the beam for loading times<br />
of 8, 15, 30, 60, 120, and 240 seconds. The maximum bending strain in the beam is<br />
calculated for the same loading times from the dimensions of the beam and the deflection of<br />
the beam. The stiffness of the beam for the loading times specified above is calculated by<br />
dividing the maximum stress by the maximum strain.<br />
5. SIGNIFICANCE AND USE<br />
5.1 The test temperature for this test is related to the temperature experienced by the<br />
pavement in the geographical area for which the asphalt binder is intended.<br />
5.2 The flexural creep stiffness or flexural creep compliance determined from this<br />
test describes the low-temperature stress-strain-time response of asphalt binder at the test<br />
temperature within the linear viscoelastic response range.<br />
5.3 The low-temperature thermal cracking performance of paving mixtures is related<br />
to the creep stiffness and the slope of the logarithm of the creep stiffness versus the<br />
logarithm of the time curve of the asphalt binder contained in the mix.<br />
5.4 The creep stiffness and the slope of the logarithm of the stiffness versus the<br />
logarithm of the time curve are used as performance-based specification criteria for asphalt<br />
binders in accordance with MP1.<br />
6. INTERFERENCES<br />
6.1 Measurements wherein the beam deflection is greater than 4.0 mm are suspect.<br />
Strains in excess of this value may exceed the linear response of asphalt binders.<br />
6.2 Measurements wherein the beam deflection is less than 0.08 mm are suspect.<br />
When the beam deflection is less than 0.08 mm, the test system resolution may not be<br />
sufficient to produce reliable test results.<br />
9
7. APPARATUS<br />
7.1 Bending Beam Rheometer (BBR) Test System--A bending beam rheometer (BBR)<br />
test system consisting of (1) a loading frame which permits the test beam, supports, and the<br />
lower part of the test frame to be submerged in a constant temperature fluid bath, (2) a<br />
controlled temperature liquid bath which maintains the test beam at the test temperature and<br />
provides a buoyant force to counterbalance the force resulting from the mass of the beam,<br />
and (3) a computer-controlled automated data acquisition component.<br />
7.1.1 Loading Frame--A frame consisting of a set of sample supports, a blunt-nosed<br />
shaft that applies the load to the midpoint of the test specimen, a load cell mounted on the<br />
loading shaft, a means for zeroing the load on the test specimen, a means for applying a<br />
constant load to the loading shaft, and a deflection-measuring transducer attached to the<br />
loading shaft. A schematic of the device is shown in figure 1.<br />
7.1.1.1 Sample Supports--Sample supports consisting of two stainless steel<br />
half-rounds 25 mm in diameter that are spaced 102 + 0.5 mm apart.<br />
7.1.1.2 Loading Shafl--A blunt-nosed loading shaft continuous with the load cell and<br />
deflection-measuring transducer that is capable of applying a preload of 30 + 5 mN and<br />
maintaining a test load of 980 + 50 mN within + 5 mN using differential air pressure or<br />
other means, such as electro-hydraulic, for adjustment. The rise time for the test load shall<br />
be less than 0.1 s, where the rise time is the time required for the load to rise from the<br />
30 5:5 mN preload to the 980 5:50 mN test load. During the rise time the system shall<br />
dampen the test load to a constant 5:5 mN value.<br />
7.1.1.3 Load Cell--A load cell with a minimum capacity of 2000 mN having a<br />
sensitivity of 1 mN, mounted in line with the loading shaft and above the fluid to measure<br />
the preload and the test load.<br />
7.1.1.4 Linear Variable Differential Transducer--A linear variable differential<br />
transducer (LVDT) or other suitable device mounted axially above the loading shaft, capable<br />
of resolving a linear movement _< 2.5/_m with a range of at least 10 mm, to measure the<br />
deflection of the test beam. Digital or analog smoothing of the load and deflection data may<br />
be required to eliminate electronic noise that could otherwise affect the ability of the second<br />
order polynomial to fit the data with sufficient accuracy to provide a reliable estimate of the<br />
m-value. Averaging five or more load or deflection signals equally spaced over a range<br />
+ 0.2 s from the reported time is acceptable to smooth the load or deflection signal.<br />
7.1.2 Controlled-Temperature Fluid Bath--A controlled-temperature liquid bath<br />
capable of maintaining the temperature at all points within the bath between -40 and 25°C<br />
within + 0.1 °C. Placing a cold specimen in the bath may cause the bath temperature to<br />
fluctuate 5: 0.2°C from the target test temperature. Consequently bath fluctuations of<br />
5: 0.2°C during testing and isothermal conditioning shall be allowed.<br />
10
7.1.2.1 Bath Fluid--A bath fluid that is not absorbed by or does not affect the<br />
properties of the asphalt binder tested.<br />
7.1.2.2 Bath Agitator--A bath agitator for maintaining the required temperature<br />
homogeneity with agitation intensity such that the fluid currents do not disturb the testing<br />
process and mechanical noise caused by vibrations is less than the resolution specified in<br />
7.1.1.4.<br />
7.1.2.3 Circulating Bath (Optional)--A circulating bath unit separate from the test<br />
frame that pumps the bath fluid through the test bath. If used, vibrations from the circulating<br />
system shall be isolated from the bath test chamber so that mechanical noise is less than the<br />
resolution specified in section 7.1.1.4.<br />
7.1.3 Data Acquisition System--A data acquisition system that resolves loads to the<br />
nearest 0.1 mN, beam deflection to the nearest 2.5 #m, and bath fluid temperature to the<br />
nearest 0.1 °C. The system shall sense the point in time when the load is fin'st applied (zero<br />
time) and, using this time as a reference, shall provide a record of subsequent load and<br />
deflection measurements relative to this time within + 0.20 s. The system shall record the<br />
load and deflection at loading times of 8, 15, 30, 60, 120 and 240 s, with less than 0.1 s<br />
between load and deflection measurement times. All readings shall be an average of five or<br />
more points within + 0.2 s from the loading time, e.g., for a loading time of 8 s, average<br />
7.8, 7.9, 8.0, 8.1 and 8.2 s.<br />
7.2 Temperature Measuring EquipmentmA calibrated temperature transducer capable<br />
of measuring the temperature to 0.1°C over the range -40 to 25°C mounted in the<br />
immediate vicinity of the midpoint of the test specimen.<br />
NOTE 1.--Required temperature measurement can be accomplished with an appropriately calibrated<br />
platinum resistance thermometer (RTD) or a thermistor. Calibration of the RTD or thermistor can be verified as per<br />
section 7.6. The RTDs meeting DIN Standard 43760 (Class A) are recommended for this purpose. The required<br />
precision and accuracy cannot be obtained unless each RTD is calibrated as a system with its respective meter or<br />
electronic circuitry.<br />
7.3 Test Beam Molds--Test beam molds of suitable dimensions to yield demolded<br />
test beams 6.35 4- 0.05 mm thick by 12.70 + 0.05 mm wide by 127 4- 0.5 mm long<br />
fabricated from aluminum flat stock as shown in figure 2, or from silicone rubber as shown<br />
in figure 3.<br />
7.4 Stainless Steel Beams--One stainless steel beam 6.4 4- 0.1 mm thick by<br />
12.7 ± 0.1 mm wide by 127 4- 0.5 mm long for measuring system compliance and one<br />
stainless steel beam 1.0 to 1.6 mm thick by 6.35 mm wide measured to 4- 0.02 mm by<br />
127 mm long measured to 4- 0.5 mm with a known stiffness modulus, for performing<br />
periodic checks on the performance of the BBR.<br />
7.5 Standard Masses--Four standard masses 50.0 or 100.0 ± 0.2 g masses for<br />
periodic BBR calibration verification.<br />
11
7.6 Calibrated Thermometers--Calibrated liquid-in-glass thermometers for<br />
verification of the temperature transducer of suitable range with subdivisions of 0.1°C. These<br />
thermometers shall be calibrated in accordance with ASTM E77. ASTM thermometers 89C<br />
and 119C are suitable thermometers.<br />
7.7 Thickness Gauge--A stepped-thickness gauge for verifying the calibration of the<br />
displacement transducer as described in figure 4.<br />
8. MATERIALS<br />
8.1 Plastic Sheeting--Clear plastic sheeting 0.12 to 0.15 mm thick, for lining the<br />
interior faces of the three long aluminum mold sections. Sheeting should not be distorted by<br />
hot asphalt binder. Transparency film sold for use with laser printers has been found<br />
suitable.<br />
8.2 Petroleum-Based Grease--A petroleum-based grease used to hold the plastic<br />
sheeting to the interior faces of the three long aluminum mold sections. (Warning: do not<br />
use any silicone-based products.)<br />
8.3 Glycerol-Talc Mixture--Used to coat the end pieces of aluminum molds.<br />
glycol,<br />
8.4 Suitable bath fluids include ethanol and glycol-methanol mixtures (e.g., 60%<br />
15 % methanol, 25 % water).<br />
9. HAZARDS<br />
9.1 Observe standard laboratory safety procedures when handling hot asphalt binder<br />
and preparing test specimens.<br />
10. PREPARATION OF APPARATUS<br />
10.1 Clean the supports, loading head and bath fluid of any particulates and coatings<br />
as necessary.<br />
NOTE 2.--Because of the brittleness of asphalt binder at the specified test temperatures, small fragments of<br />
asphalt binder can be introduced into the bath fluid. If these fragments are present on the supports or the loading<br />
head, they will affect the measured deflection. Because of their small size, the fragments will deform under load and<br />
add an apparent deflection to the true deflection of the beam. Filtration of the bath fluid will aid in preserving the<br />
required cleanliness.<br />
10.2 Select the test temperature and adjust the bath fluid to the selected temperature.<br />
Wait until the temperature stabilizes and then allow the bath to equilibrate to the test<br />
temperature + 0.2°C.<br />
10.3 Activate the data acquisition system and load the software as explained in the<br />
manufacturer's manual for the test system.<br />
12
11. STANDARDIZATION<br />
11.1 Verify calibration of the displacement transducer, load cell, and temperature<br />
transducer. Conduct each of the steps in this section each day before conducting any tests.<br />
NOTE 3.--Calibration is usually performed by a calibration service agency. Calibration verification and<br />
quality checks may be performed by the manufacturer, other agencies providing such services, or in-house personnel<br />
using the procedures described below.<br />
11.1.1 Verify calibration of the displacement transducer using a stepped thickness<br />
gauge of known dimensions similar to the one shown in figure 4. Remove the loading frame<br />
from the bath. Place the gauge on a reference platform underneath the loading shaft. Measure<br />
the rise of the steps relative to the top surface of the gauge with the displacement transducer.<br />
Compare the measured values with the known dimensions of the gauge. If the difference is<br />
> 4/zm, further calibration or maintenance is required. Report the calibration constants<br />
(#m/mV) for the displacement transducers to three significant figures. The calibration<br />
constants should be repeatable from day to day. Otherwise, the operation of the system may<br />
be suspect.<br />
11.1.2 Verify calibration of the load cell using four standard dead masses evenly<br />
distributed over the range of the load cell. Perform the verification by resting the loading<br />
shaft against the 6.35-mm thick standard steel beam, loading it with the four standard masses<br />
sequentially in four steps, while recording the load after each step. If the load indicated by<br />
the data acquisition system does not agree with the force imposed by the standard masses<br />
within + 2 mN at all steps, further calibration or maintenance is required. Report the<br />
calibration constants (mN/m) for the load transducers to three significant figures. The<br />
calibration constants should be repeatable from day to day. Otherwise, the operation of the<br />
system may be suspect.<br />
11.1.3 Verify calibration of the temperature detector by using a calibrated<br />
thermometer of suitable range meeting the requirements of section 7.6. Immerse the<br />
thermometer in the liquid bath close to the thermal detector and compare the temperature<br />
indicated by the calibrated thermometer to the detector signal being displayed. If the<br />
temperature indicated by the thermal detector does not agree with the liquid-in-glass<br />
thermometer within + 0.1 °C, further calibration or maintenance is required.<br />
11.2 Determine the compliance of the loading system by placing the 6.35-mm-thick<br />
stainless steel beam on the testing supports, resting the loading tip of the loading shaft<br />
against the stainless steel beam, and applying a load to the shaft of 980 + 50 mN measured<br />
to the nearest 2 mN. The beam is relatively rigid within the range of loading applied and the<br />
range of deflection measurement specified. Therefore, any measured deflection is caused by<br />
the load cell or other parts of the test system. Divide the deflection measured under this load<br />
by the applied load. The quotient is the compliance of the loading system in/_m/mN. Use<br />
this result to calculate the deflection component that is not due to the compliance of the<br />
system. This component is automatically subtracted from the deflection measured during a<br />
test.<br />
13
11.3 Perform a daily quality control check on the operation of the overall system<br />
using the 1.0- to 1.6-mm-thick stainless steel beam of known modulus. Load the steel beam<br />
with 981 and 1961 mN using the standard masses (100 and 200 g) and measure the deflection<br />
at the midpoint. Using the load applied and deflection measured, calculate the elastic<br />
modulus of the beam. Compare the calculated modulus to the known modulus of the beam. If<br />
the calculated modulus differs from the known modulus by 10% or more, the operation of<br />
the system is suspect. Perform required maintenance on the system and then repeat section<br />
11.<br />
12. PREPARATION OF MOLDS AND TEST SPECIMENS<br />
12.1 To prepare aluminum molds, spread a very thin layer of petroleum-based<br />
grease, only sufficient to hold the plastic strips to the aluminum, on the interior faces of the<br />
three long aluminum mold sections. Place the plastic strips over the aluminum faces and rub<br />
the plastic with firm finger pressure. Assemble the mold as shown in figure 2 using the<br />
rubber 0-rings to hold the pieces of the mold together. Inspect the mold and press the plastic<br />
film against the aluminum to force out any air bubbles. If air bubbles remain, disassemble<br />
the mold and recoat the aluminum faces with grease. Cover the inside faces of the mold's<br />
two end pieces with a thin film of glycerol to prevent the asphalt binder from sticking to the<br />
aluminum end pieces. After assembly, keep the mold at room temperature until pouring the<br />
asphalt binder.<br />
12.2 To prepare silicone rubber molds, assemble the two mold sections.<br />
12.3 If unaged binder is to be tested, obtain test samples according to T40.<br />
12.4 Heat the material until it is sufficiently fluid to pour.<br />
NOTE 4.--Minimum pouring temperatures that produce a consistency equivalent to that of SAE 10W30<br />
motor oil (readily pours but not overly fluid) at room temperature are recommended. Heating unaged asphalt binders<br />
to temperatures above 135°C should be avoided. Some modified asphalts or heavily aged binders,however, may<br />
require pouring temperatures above 135°C may be required. PAV residues shall be placed in TFOT pans and may<br />
be heated up to 163°C. In all cases, heating time should be minimized. These precautions avoid oxidative hardening<br />
and volatile loss that will further harden the sample. During the heating process, the sample should be covered and<br />
stirred occasionally to ensure homogeneity.<br />
12.5 Molding (aluminum mold)--If an aluminum mold is used, begin pouring the<br />
binder from one end of the mold and move toward the other end, slightly overfilling the<br />
mold. When pouring, hold the sample container 20 to 100 mm from the top of the mold and<br />
pour continuously toward the other end in a single pass. After pouring, allow the mold to<br />
cool 45 to 60 minutes to room temperature. Trim the exposed face of the cooled specimens<br />
flush with the top of the mold using a hot knife or a heated spatula. Discard the plastic<br />
sheeting (lining the mold sections) if it becomes distorted.<br />
12.6 Molding (silicone rubber mold)--If a silicone rubber mold is used, fill the mold<br />
from the top of the mold in a slow, steady manner, taking care not to entrap air bubbles. Fill<br />
14
the mold to the top with no appreciable overfilling. After pouring, allow the mold to cool to<br />
room temperature for at least 45 minutes.<br />
12.7 Store all test specimens in their molds at room temperature prior to testing.<br />
Schedule testing so that it is completed within 4 hours after specimens are poured.<br />
NOTE 5.--Time-dependent increases in stiffness can occur when asphalt binders are stored at room<br />
temperature for even short periods of time. This increase in stiffness is the result of molecular associations and is<br />
referred to as steric hardening in the literature.<br />
12.8 Just prior to testing, cool the aluminum or silicone mold containing the test<br />
specimen in a freezer or ice bath at -5°C + 5°C for 5 to 10 minutes, only long enough to<br />
stiffen the asphalt binder beam so that it can be readily demolded without distortion (note 6).<br />
Some softer grades may require lower temperatures. Do not cool the molds containing the<br />
specimens in the test bath because it may cause temperature fluctuations in the bath to exceed<br />
+ 0.2°C.<br />
NOTE6.--Excessive<br />
variability in the test data.<br />
cooling may cause unwanted hardening of the beam, thereby causing increased<br />
12.9 Immediately demold the specimen when it is sufficiently stiff to demold without<br />
distortion by disassembling the aluminum mold or by removing the test specimen from the<br />
silicone rubber mold.<br />
NOTE7.--Minimize distortion of the specimen during demolding. Full contact at specimen supports is<br />
assumed in the analysis. A warped test beam yields a measured stiffness less than the actual stiffness.<br />
13. PROCEDURE<br />
13.1 When testing a specimen for compliance with MP1, select the appropriate test<br />
temperature from table 1 of MP1. After demolding, immediately place the test specimen in<br />
the testing bath and condition it at the testing temperature for 60 + 5 minutes.<br />
NoTE 8.--Asphalt binders may harden rapidly when held at low temperatures. This effect, which is called<br />
physical hardening, is reversible when the asphalt binder is heated to room temperature or slightly above. Because of<br />
physical hardening, conditioning time must be carefully controlled if repeatable results are to be obtained.<br />
13.2 After conditioning, place the test beam on the test supports and initiate the test.<br />
Maintain the bath at test temperature + 0.2°C during testing.<br />
13.3 Enter the specimen identification information, test load, test temperature, time<br />
the specimen is placed in bath test temperature, and other information as appropriate into the<br />
computer that controls the test system.<br />
13.4 Manually apply a 30 + 5 mN preload to the beam to ensure contact between<br />
the beam and the loading head.<br />
15
NOTE9.--The specified preload on the specimen is required to ensure continuous contact between the<br />
loading shaft and the specimen. Failure to establish continuous contact within the required load range gives<br />
misleading results.<br />
13.5 Activate the automatic test system that is programmed to proceed as follows.<br />
13.5.1 Apply a 980 + 50 mN initial seating load for 1 + 0.1 second.<br />
NOTE 10.--The actual load on the beam as measured by the load cell is used in calculating the stress in the<br />
beam. The 980 + 50 mN initial seating and test load includes the 30 + 5 mN preload.<br />
13.5.2 Reduce the load to 30 + 5 mN and allow the beam to recover for 20 + 0.1<br />
seconds.<br />
NOTE 11.--The initial seating loads described in sections 13.5.1 and 13.5.2 are applied and removed<br />
automatically by the computer-controlled loading system and are transparent to the operator. Data are not recorded<br />
during initial loading.<br />
13.5.3 Apply a test load ranging from 980 + 50 mN, and maintain the load constant<br />
to + 5 mN for 240 s.<br />
13.5.4 Remove the test load and terminate the test.<br />
13.5.5 At the end of the initial seating, load and at the end of the test, monitor the<br />
computer screen to verify that the load on the beam in each case returns to 30 + 5 mN.<br />
13.6 Remove the specimen from the supports and proceed to the next test.<br />
14. CALCULATION AND INTERPRETATION OF RESULTS<br />
See Annex.<br />
15. REPORT<br />
15.1 Report data as shown in figure A1 that describes individual tests, including:<br />
15.1.1 Temperature of the test bath measured 60 s after the test load is first applied,<br />
to the nearest 0.1 °C;<br />
16<br />
15.1.2 Date and time when test load is applied;<br />
15.1.3 File name of test data;<br />
15.1.4 Name of operator;<br />
15.1.5 Sample identification number;
15.1.6 Any flags issued by software during test;<br />
15.1.7 Correlation coefficient, R2 for log stiffness versus log time, expressed to<br />
nearest 0.000001;<br />
15.1.8 Anecdotal comments (maximum 256 characters);<br />
15.1.9 Report constants A, B, and C to three significant figures;<br />
15.1.10 Difference between measured and estimated stiffness calculated as:<br />
(Measured-Estimated)<br />
x 100% / Estimated<br />
15.2 Report data as shown in figure A1 for time intervals of 8, 15, 30, 60, 120, and<br />
240 seconds including:<br />
15.2.1 Time beam is placed in bath;<br />
15.2.2 Time test started;<br />
15.2.3 Loading time, to the nearest 0.1 second;<br />
15.2.4 Load, to the nearest 0.1 mN;<br />
15.2.5 Beam deflection, to the nearest 2 #m;<br />
15.2.6 Measured Stiffness modulus, in MPa, expressed to three significant figures;<br />
15.2.7 Estimated Stiffness modulus, in MPa, expressed to three significant figures;<br />
15.2.8 Estimated m, to the nearest 0.001.<br />
16. PRECISION AND BIAS<br />
16.1 Precision--The research required to develop precision values in accordance with<br />
ASTM C802 has not been conducted.<br />
16.2 Bias--The research required to establish the bias of this method has not been<br />
conducted.<br />
17. KEY WORDS<br />
Bending beam rheometer, flexural creep compliance, flexural creep stiffness.<br />
17
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22
ANNEX<br />
1.1 A typical test result is shown in figure A1. Disregard measurements obtained and<br />
the curves projected on the computer screen during the initial 8 s application of the test load.<br />
Data from a creep test obtained immediately after the application of the test load may not be<br />
valid because of dynamic loading effects and the finite rise time. Use only the data obtained<br />
between 8 and 240 s loading time for calculating S(t) and m.<br />
1.2 Deflection of an elastic beam--Using the elementary bending theory, the<br />
midpoint deflection of an elastic prismatic beam of constant cross section loaded in threepoint<br />
loading can be obtained by applying equations (1) and (2) as follows:<br />
where<br />
6 = PL3/48EI<br />
(1)<br />
t5 = deflection of beam at the midpoint,<br />
P = load applied, N<br />
L = span length, mm<br />
E = modulus of elasticity, MPa<br />
I = moment of inertia, mm4<br />
and<br />
mm<br />
where<br />
I = bh3/12 (2)<br />
I = moment of inertia of cross section of test beam, mm4<br />
b = width of beam, mm<br />
h = thickness of beam, mm<br />
NOTE 12.--The test specimen has a span-to-depth ratio of 16 to 1 and the contribution of shear to deflection<br />
of the beam can be neglected.<br />
1.3 Elastic flexural modulus--According to elastic theory, calculate the flexural<br />
modulus of a prismatic beam of constant cross section loaded at its midpoint thus:<br />
where<br />
E = pL3/4bh3_ (3)<br />
E = time-dependent flexural creep stiffness, MPa<br />
P = constant load, N<br />
L = span length, mm<br />
b = width of beam, mm<br />
h = depth of beam, mm<br />
it = deflection of beam, mm<br />
23
1.4 Maximum bending stress--The maximum bending stress in the beam occurs at the<br />
midpoint at the top and bottom of the beam. Calculate tr thus:<br />
where<br />
o = maximum bending stress in beam, MPa<br />
P = constant load, N<br />
L = span length, mm<br />
b = width of beam, mm<br />
h = depth of beam, mm<br />
a = 3PL/2bh 2 (4)<br />
1.5 Maximum bending strain--The maximum bending strain in the beam occurs at<br />
the midpoint at the top and bottom of the beam. Calculate e thus:<br />
where<br />
= 6_h/L2 mm/mm (5)<br />
= maximum bending strain in beam, mm/mm<br />
= deflection of beam, mm<br />
h = thickness of beam, mm<br />
L = span length, mm<br />
1.6 Linear Viscoelastic Stiffness Modulus--According to the elastic-viscoelastic<br />
correspondence principle, it can be assumed that if a linear viscoelastic beam is subjected to<br />
a constant load applied at t = 0 and held constant, the stress distribution is the same as that<br />
in a linear elastic beam under the same load. Further, the strains and displacements depend<br />
on time and are derived from those of the elastic case by replacing E with 1/D(t). Since<br />
1/D(t) is equivalent to S(t), rearranging the elastic solution results in the following<br />
relationship for the stiffness:<br />
where<br />
S(t) = pL3/4bh3i_(t) (6)<br />
S(t) = time-dependent flexural creep stiffness, MPa<br />
P = constant load, N<br />
L = span length, mm<br />
b = width of beam, mm<br />
h = depth of beam, mm<br />
6(t) = deflection of beam, mm, and<br />
iS(t) and S(t) indicate that the deflection and stiffness, respectively,<br />
are functions of time.<br />
24
1.7 Presentation of Data<br />
1.7.1 Plot the response of the test beam to the creep loading as the logarithm of<br />
stiffness with respect to the logarithm of loading time. A typical representation of test data is<br />
shown in figure A2. Over the limited testing time from 8 to 240 s, the plotted data shown in<br />
figure A2 can be represented by a second order polynomial as follows:<br />
log S(t) = A + B[log(t)] + C[log(t)] 2 (7)<br />
and, the slope, m, of the logarithm of stiffness versus logarithm time curve is equal to<br />
(absolute value):<br />
where<br />
S(t) = time-dependent<br />
t = time in seconds<br />
A, B, and C = regression coefficients<br />
[m(t)[ = d[log S(t)]/d[log(t)] = B + 2C[log(t)] (8)<br />
flexural creep stiffness, MPa<br />
Smoothing the data may be required to obtain smooth curves for the regression analysis as<br />
required to determine an m value. This can be done by averaging 5 readings taken at the<br />
reported time + 0.1 and :1:0.2 seconds.<br />
1.7.2 Obtain the constants A, B, and C from the least squares fit of equation 7. Use<br />
data equally spaced with respect to the logarithm of time to determine the regression<br />
coefficients in equations 7 and 8. Determine experimentally the stiffness values used for the<br />
regression to derive the coefficients A, B, and C and to, in turn, calculate values of m after<br />
loading times of 8, 15, 30, 60, 120, and 240 s.<br />
1.8 Calculation of Regression Coefficients, estimated stiffness values and m.<br />
1.8.1 Calculate the regression coefficients A, B, and C in equations 7 and 8 and the<br />
denominator D as follows:<br />
a = [Sy(Sx2ax4- Sx32) - Sxy(SxlSx4- S_2Sx3)+ S_(SxlS_3 - Sx22)]/D (9)<br />
B = [6(S_oS,4- S,.¢_x3) - S,,(SySx4 - S_Sa) + Sa(SySx3 - SxySa)] / D (10)<br />
C = [6(S_aS_ - Sx3S_) - S,,(S_,S_ - S,3Sy) + Sx2(S_,Sxy- Sx2Sy)]/D (11)<br />
D = 6(S_aSx4- S_32)- S_I(SxlS_4- S_2S_3 ) + S_2(S_1S_3- Sx22) (12)<br />
where, for loading times of 8, 15, 30, 60, 120, and 240 seconds:<br />
Sxa = log 8 + log 15 + ... log 240<br />
Sxz = (log 8)2 + (log 15)2 + ... (log 240) 2<br />
S_3 = (log 8)3 + (log 15)3 + ... (log 240) 3<br />
S_4 = (log 8)4 + (log 15) 4 + ... (log 240) 4<br />
25
Sy = log S(8) + log S(15) + ... log S (240)<br />
S_y = log S(8)(log (8)) + log S(15) log (15) + ... log S(240) log (240)<br />
S_= [log (8)] 2 log S(8) + [log (15)] 2 log S(15) + ... [log (240)] 2 log S(240)<br />
1.8.2 Calculate the estimated stiffness at 8, 15, 30, 60, 120, and 240 seconds as:<br />
logS(t) = A + B[log(t)] + C[log(t)] 2 (13)<br />
1.8.3 Calculate the estimated m value at 8, 15, 30, 60, 120, and 240 s as the<br />
absolute value of<br />
[m] = B 2C[log(t)] (14)<br />
1.8.4 Calculate the fraction of the variation in the stiffness explained by the quadratic<br />
model as:<br />
R z = 1.00 - [l°gS(8)-l°gS(8)]2 + ""[l°gS(240)-l°gS(240)]2]<br />
[logS(8)-log(S)l 2 + ...[logS(240)-log(S)] 2 ]<br />
(15)<br />
as:<br />
1.8.5 Calculate S the average of the stiffness values at 8, 15, 30, 60, 120, and 240 s<br />
log -S = [logS(8) + ...logS(240)]/6 (16)<br />
1.8.6 Use the estimated values of the stiffness and m at 60 s for specification<br />
purposes. Measured and estimated stiffness values should agree to within 2 %. Otherwise, the<br />
test is considered suspect.<br />
26
Test Information<br />
Project: testing Target Temp: 23.0°C Conf. Test: 2.199e+008<br />
Operator: jsy Actual Temp: 14.8°C Date: 09/17/93<br />
Specimen: plastic beam b Soak Time: 0.0 sec Load Const: 0.24<br />
Time: 11:47:03 Beam Width: 12.70 mm Deft Const: 0.0024<br />
Date: 09/18/93 Thickness: 6.35 mm Date: 09/17/93<br />
File: 0818934.DAT<br />
Results<br />
t P d Measured Estimated<br />
Time Force Deft<br />
Stiffness Stiffness<br />
Difference m-value<br />
(see) (N) (ram) (kPa) (kPa) %<br />
8 .9859 .9126 87030.0 87060.0 .03532 O.176<br />
15 .9894 1.022 77990.0 77930.0 -.08120 O.175<br />
30 .9913 1.158 68960.0 68990.0 .04809 O.175<br />
60 .9910 1.308 61110.0 61110.0 .004487 0.174<br />
120 .9908 1.475 54150.0 54150.0 -.001551 O.174<br />
240 .9906 1.664 48010.0 48000.0 -.005077 O.174<br />
Regression Coefficients:<br />
a = 5.100 b = -. 1784 c = .001020 R^2 = 0.999996<br />
Figure A1<br />
Typical Test Report<br />
27
Z<br />
1.3<br />
1.2<br />
1.1 , , ....<br />
J<br />
1 • '; "<br />
09. .....<br />
0.8 ....<br />
0.7 , '<br />
0.6<br />
0.5<br />
0.4 "<br />
0.3 ' "<br />
0.2 ....... =<br />
0.1<br />
I<br />
iii<br />
il l _ i<br />
-0.1 -<br />
-30 0 30 60 90 120 150 180 210 240 270<br />
Loading Time, s<br />
_ ,<br />
3.5<br />
_ i i i i i<br />
2.5 ......<br />
d 2 ....<br />
1.5 ...... _ _"-- ,,,<br />
0.5 -f'_ _"- ii w i ii •<br />
¢<br />
0 ii i<br />
-0.5<br />
i n _ ii i<br />
-1<br />
- 30 0 30 60 90 120 150 180 210 240 270<br />
Loading Time, s<br />
Figure A2 Typical Load and Deflection Plots for the Bending Beam Rheometer<br />
28
Standard Method of Test for<br />
Determining the Rheological Properties<br />
of Asphalt Binder Using a<br />
Dynamic Shear Rheometer (DSR)<br />
AASHTO Designation: TP51<br />
1. SCOPE<br />
1.1 This test method covers the determination of the dynamic shear modulus and<br />
phase angle of asphalt binder when tested in dynamic (oscillatory) shear using parallel plate<br />
test geometry. It is applicable to asphalt binders that have dynamic shear modulus values<br />
from 100 Pa to 10 MPa. This range in modulus is typically obtained between 5°C and 85°C.<br />
This test method is intended for determining the linear viscoelastic properties of asphalt<br />
binders as required for specification testing and is not intended as a comprehensive procedure<br />
for the full characterization of the viscoelastic properties of asphalt binder.<br />
1.2 This standard is appropriate for unaged material or material aged in accordance<br />
with T240, T179, or PP1.<br />
1.3 Particulate material in the asphalt binder is limited to particles with longest<br />
dimensions less than 250 #m.<br />
1.4 The values stated in SI units are to be regarded as the standard.<br />
1.5 This standard may involve hazardous materials, operations, and equipment. This<br />
standard does not purport to address all of the safety problems associated with its use. It is<br />
the responsibility of the user of this procedure to establish appropriate safety and health<br />
practices and to determine the applicability of regulatory limitations prior to use.<br />
2. REFERENCE DOCUMENTS<br />
2.1 AASHTO Standards<br />
MP1 Test Method for Performance-Graded Asphalt Binder<br />
T40 Practice for Sampling Bituminous Materials<br />
T179 Test Method for Effect of Heat and Air on Asphalt Materials (Thin Film Oven<br />
Test)<br />
This standardis basedon <strong>SHRP</strong>Product1007.<br />
29
T240 Test Method for Effect of Heat and Air on a Moving Film of Asphalt (Rolling<br />
Thin Film Oven Test)<br />
TP1 Test Method for Determining the Flexural Creep Stiffness of an Asphalt<br />
Binder Using the Bending Beam Rheometer<br />
PP1 Practice for Accelerated Aging of an Asphalt Binder Using a Pressurized<br />
Aging Vessel<br />
PP6 Practice for Grading or Verifying the Performance Grade of an Asphalt Binder<br />
2.2 ASTM Standards<br />
E1 Specification for ASTM Thermometers<br />
E220 Method for Calibration of Thermocouples by Comparison Techniques<br />
2.3 DIN Standards<br />
43760<br />
3. TERMINOLOGY<br />
3.1 Definitions<br />
3.1.1 asphalt binder, n--an asphalt-based cement that is produced from petroleum<br />
residue either with or without the addition of non-particulate organic modifiers.<br />
3.2 Descriptions of Terms Specificto this Standard<br />
3.2.1 complex shear modulus, G*--ratio calculated by dividing the absolute value of<br />
the peak-to-peak shear stress, 7-,by the absolute value of the peak-to-peak shear strain, 3,.<br />
3.2.2 phase angle, _5--the angle in radians or degrees between a sinusoidally applied<br />
strain and the resultant sinusoidal stress in a controlled-strain testing mode, or between the<br />
applied stress and the resultant strain in a controlled-stress<br />
testing mode.<br />
3.2.3 loss shear modulus, G"--the complex shear modulus multiplied by the sine of<br />
the phase angle expressed in degrees. It represents the component of the complex modulus<br />
that is a measure of the energy lost (dissipated during a loading cycle).<br />
3.2.4 storage shear modulus, G'--the complex shear modulus multiplied by the<br />
cosine of the phase angle expressed in degrees. It represents the in-phase component of the<br />
complex modulus that is a measure of the energy stored during a loading cycle.<br />
3.2.5 parallel plate geometry, n--a testing geometry in which the test sample is<br />
sandwiched between two relatively rigid parallel plates and subjected to oscillatory shear.<br />
3O
3.2.6 oscillatory shear, n--refers to a type of loading in which a shear stress or shear<br />
strain is applied to a test sample in an oscillatory manner such that the shear stress or strain<br />
varies in amplitude about zero in a sinusoidal manner.<br />
3.2.7 linear viscoelastic, adj--refers to a region of behavior in which the dynamic<br />
shear modulus is independent of shear stress or strain.<br />
3.2.8 molecular association, n--refers to associations that occur between asphalt<br />
binder molecules during storage at ambient temperature. Often referred to as steric hardening<br />
in the asphalt literature, molecular associations can increase the dynamic shear modulus of<br />
asphalt binders. The extent of molecular association is asphalt specific and may be apparent<br />
even after a few hours of storage.<br />
4. SUMMARY OF TEST METHOD<br />
4.1 This standard contains the procedure used to measure the complex shear modulus<br />
(G*) and phase angle (6) of asphalt binders using a dynamic shear rheometer and parallel<br />
plate test geometry.<br />
4.2 The standard is suitable for use when the dynamic shear modulus varies between<br />
100 Pa and 10 MPa. This range in modulus is typically obtained between 5°C and 85°C,<br />
dependent upon the grade, test temperature, and conditioning (aging) of the asphalt binder.<br />
4.3 Test specimens 1 mm thick by 25 mm in diameter, or 2 mm thick by 8 mm in<br />
diameter, are formed between parallel metal plates. During testing, one of the parallel plates<br />
is oscillated with respect to the other at preselected frequencies and rotational deformation<br />
amplitudes (or torque amplitudes). The required amplitude depends upon the value of the<br />
complex shear modulus of the asphalt binder being tested. The required amplitudes have been<br />
selected to ensure that the measurements are within the region of linear behavior.<br />
4.4 The test specimen is maintained at the test temperature + 0.1°C by positive<br />
heating and cooling of the upper and lower plates.<br />
4.5 Oscillatory loading frequencies using this standard can range from 1 to 100 rad/s<br />
using a sinusoidal waveform. Specification testing is performed at a test frequency of<br />
10 rad/s. The complex modulus (G*) and phase angle (iS)are calculated automatically as part<br />
of the operation of the rheometer using proprietary computer software supplied by the<br />
equipment manufacturer.<br />
5. SIGNIFICANCE AND USE<br />
5.1 The test temperature for this test is related to the temperature experienced by the<br />
pavement in the geographical area for which the asphalt binder is intended.<br />
31
5.2 The complex shear modulus is an indicator of the stiffness or resistance of<br />
asphalt binder to deformation under load. The complex shear modulus and the phase angle<br />
define the resistance to shear deformation of the asphalt binder in the linear viscoelastic<br />
region. Other linear viscoelastic properties, such as the storage modulus (G'), or the loss<br />
modulus (G"), can be calculated from the complex modulus and the phase angle. The loss<br />
modulus is a measure of the energy dissipated during each loading cycle.<br />
5.3 The complex modulus and the phase angle are used to calculate performancerelated<br />
criteria in accordance with MP1.<br />
6. APPARATUS<br />
6.1 Dynamic Shear Rheometer Test System--A dynamic shear rheometer test system<br />
consisting of parallel metal plates, an environmental chamber, a loading device, and a control<br />
and data acquisition system.<br />
6.1.1 Testplates--Metal test plates with smooth polished surfaces. One 8.00 + 0.05<br />
mm in diameter and one 25.00 + 0.05 mm in diameter. The base plate in some rheometers<br />
is a flat plate. A raised portion 2 to 5 mm high with the same radius as the upper plate is<br />
recommended. The raised portion makes it easier to trim the specimen and may improve test<br />
repeatability.<br />
6.1.2 Environmental Chamber--A chamber for controlling the test specimen<br />
temperature, by heating (in steps or ramps), or cooling (in steps or ramps), to maintain a<br />
constant specimen environment. The medium for heating and cooling the specimen in the<br />
environmental chamber is a gas or liquid (note 1) that will not affect asphalt binder<br />
properties. The temperature in the chamber may be controlled by the circulation of fluid or<br />
conditioned gas; nitrogen or water is acceptable. When air is used, a suitable drier must be<br />
included to prevent condensation of moisture on the plates and fixtures and, if operating<br />
below freezing, the formation of ice. The environmental chamber and the temperature<br />
controller shall control the temperature of the specimen, including thermal gradients within<br />
the sample, to an accuracy of + 0.1 °C. The chamber shall completely enclose the top and<br />
the bottom plates to minimize thermal gradients.<br />
NOTE1.--A circulating bath unit separate from the dynamic shear rheometer which pumps the bath fluid<br />
through the test chamber may be required if a fluid medium is used.<br />
6.1.2.1 Temperature Controller--A temperature controller capable of maintaining<br />
specimen temperatures within 0.1 °C for test temperatures ranging from 5 to 85°C.<br />
6.1.2.2 Temperature Detector--A reference thermal detector (RTD) mounted inside<br />
the environmental chamber, in intimate contact with the fixed plate, with a range of 5 to<br />
85°C, readable and accurate to the nearest 0.1°C. This detector shall be used to control the<br />
temperature in the chamber and provide a continuous readout of temperature during the<br />
mounting, conditioning, and testing of the specimen.<br />
32
NOTE2.--Platinum RTDs meeting DIN Standard 43760 (Class A) or equal are recommended for this<br />
purpose. The RTD shall be calibrated as an integral unit with its respective meter or electronic circuitry.<br />
6.1.2.3 Reference Temperature Sensing Device--A thermistor, RTD, or<br />
thermocouple as described in sections 9.1.1.2.1, 9.1.1.2.2, or 9.1.1.2.3 shall be used.<br />
6.1.3 Loading device--The loading device shall apply a sinusoidal oscillatory load to<br />
the specimen at a frequency of 10.0 + 0.1 rad/s. If frequencies other than 10 rad/s are used,<br />
the frequency shall be accurate to 1%. The loading device shall be capable of providing<br />
either a stress-controlled or strain-controlled load. If the load is strain controlled, the loading<br />
device shall apply a cyclic torque sufficient to cause an angular rotational strain accurate to<br />
within 100 #rad of the strain specified. If the load is stress controlled, the loading device<br />
shall apply a cyclic torque accurate to within 10 mN.m of the torque specified. Total system<br />
compliance at 100 N.m torque shall be < 2 mrad/N.m.<br />
6.1.4 Control and Data Acquisition System--The control and data acquisition system<br />
shall provide a record of temperature, frequency, deflection angle and torque. Devices used<br />
to measure these quantities shall meet the accuracy requirements specified in table 1. In<br />
addition, the system shall calculate and record the shear stress, shear strain, complex shear<br />
modulus (G*) and phase angle (iS).The system shall measure and record G*, in the range of<br />
100 Pa to 10 MPa, to an accuracy of 0.5% or less. The system shall measure and record the<br />
phase angle, in the range from 0 to 90 °, + 0.1 °<br />
Table 1. Control and Data Acquisition<br />
System Requirements<br />
Quantity<br />
Accuracy<br />
Temperature 0.1 °C<br />
Frequency 1%<br />
Torque<br />
Deflection angle<br />
10 mN.m<br />
100 #rad<br />
6.2 Specimen Mold (Optional)--A silicone rubber mold for forming asphalt binder<br />
test specimens having a diameter approximately equal to the diameter of the upper test plate<br />
and a height approximately equal to 1.5 times the width of the test gap.<br />
wide.<br />
6.3 Specimen Trimmer--A specimen trimmer with a straight edge at least 4 mm<br />
6.4 Calibrated Temperature Detector--A calibrated thermocouple, thermistor, or<br />
RTD with a thickness or diameter < 2.0 mm is suitable for measuring the temperature of a<br />
dummy specimen or sample of asphalt binder. Thermocouples and thermistors are not<br />
reliable to -1-0.1 °C unless calibrated to a standard traceable to the National Institute of<br />
Standards and Technology (NIST) and must be calibrated with associated meters or electronic<br />
circuitry. Platinum RTDs are typically not suitable because they are too large to fit in the gap<br />
between the test plates in the DSR.<br />
33
7. HAZARDS<br />
7.1 Standard laboratory caution should be used in preparing the test specimens of the<br />
hot asphalt binder.<br />
8. PREPARATION OF APPARATUS<br />
8.1 Prepare the apparatus for testing in accordance with the manufacturer's<br />
recommendations. Specific requirements will vary for different DSR models and<br />
manufacturers.<br />
8.2 Mount the test plates on the test fixtures and tighten fLrmly.<br />
8.3 Select the testing temperature according to the grade of the asphalt binder or<br />
according to the preselected testing schedule (note 3). Allow the DSR to reach a stabilized<br />
temperature + 0.1 °C of the test temperature.<br />
NOTE3.--Specification<br />
MP1 and Practice PP6 provide guidance on the selection of test temperatures.<br />
8.4 With the test plates at the test temperature or the middle of the expected testing<br />
range, establish the zero gap level by one of two methods. One method is to manually spin<br />
the moveable plate. While the moveable plate is spinning, close the gap until the movable<br />
plate touches the fixed plate. The zero gap is reached when the plate stops spinning<br />
completely. The other method, for rheometers with normal force transducers, is to close the<br />
gap and observe the normal force. After establishing contact between the plates, set the zero<br />
gap at approximately zero normal force.<br />
8.5 Move the plates apart and establish a gap setting of 1 mm plus 0.05 mm (for<br />
25-mm diameter test specimens) or 2 mm plus 0.05 mm (for 8-mm diameter test specimens).<br />
NoTE 4.--The frame, detectors, and fixtures in the DSR change dimension with temperature, which causes<br />
the zero gap. Adjustments in the gap are not necessary when measurements are made over a limited range of<br />
temperatures. The gap should be set with the test apparatus at the test temperature. When tests are to be conducted<br />
over a range of temperatures, the gap should be set with the test apparatus at the middle of the expected range of test<br />
temperatures. For most instruments, no gap adjustment is needed if the test temperature will be + 120C of the<br />
temperature at which the gap is set.<br />
9. CALIBRATION AND STANDARDIZATION<br />
9.1 Perform the following calibration and verification procedures at least every six<br />
months:<br />
9.1.1 Temperature--Prepare a dummy specimen of asphalt binder or use a silicone<br />
wafer following standard procedures. Use the dummy specimen only for temperature<br />
verification measurements. (Dynamic shear measurements are not valid if a temperature<br />
34
detector is inserted into the asphalt binder.) Verify the specimen temperature indicated by the<br />
DSR RTD in trial runs by using a calibrated temperature detector inserted into the dummy<br />
specimen.<br />
9.1.1.1 Compare temperature measurements obtained from the dummy specimen and<br />
the DSR RTD. Use the temperature measured inside the dummy specimen as the reference<br />
temperature. If the temperatures are not equal, apply an appropriate temperature correction to<br />
the temperature measurement indicated by the DSR RTD.<br />
9.1.1.2 Thermal gradients within the rheometer and the difficulty of calibrating the<br />
instrument RTD while it is mounted in the rheometer (see note 5) require a direct<br />
measurement of the temperature between the plates using a dummy specimen and a reference<br />
temperature sensing device. This is accomplished by placing a dummy specimen between the<br />
plates and reading the temperature in the dummy specimen with a reference temperature<br />
sensing device. A thermistor, RTD, or thermocouple as described in sections 9.1.1.2.1,<br />
9.1.1.2.2, or 9.1.1.2.3 shall be used as the reference temperature sensing device. Adjust the<br />
temperature in the chamber to the minimum temperature that will be used for testing and<br />
allow the chamber to come to thermal equilibrium. Read the instrument RTD and the<br />
temperature of the dummy specimen. Increase the temperature in increments of no more than<br />
6°C and repeat the measurements to cover the range of test temperatures. Using these<br />
measurements, obtain the temperature difference between the instrument RTD and the<br />
reference temperature sensing device inserted between the plates. This difference will not be<br />
a constant but will vary with test temperature. Offset the thermal controller on the rheometer<br />
so that the target test temperature is obtained between the plates.<br />
NOTE 5.--The RTD and its meter can be calibrated by a commercial vendor. Verification of calibration can<br />
be obtained by comparing the output from the RTD with a calibrated ASTM mercury-in-glass thermometer in<br />
accordance with ASTM E220. A stirred water bath is suitable for calibrating the thermal detector. Select a partial<br />
immersion mercury-in-glass thermometer with an appropriate range (ASTM 90C; 0 to 30°C or ASTM 91C; 20 to<br />
50°C) and place the thermal detector and the thermometer in the stirred water bath. Fasten the detector to the glass<br />
thermometer with a rubber band or rubber O-ring. Allow the bath, detector, and thermometer to come to thermal<br />
equilibrium and record the temperature of the glass thermometer and the readout from the thermal detector. The<br />
temperature in the bath shall be constant to within 0.1 degree.<br />
9.1.1.2.1 A silicone wafer 2 mm thick by 25 mm in diameter containing a thermistor<br />
calibrated to the nearest 0.1 °C shall be inserted between the plates as the dummy specimen.<br />
Use a thin coating of petroleum jelly to ensure good thermal contact. A suitable thermistor<br />
mounted in a silicone wafer is available from Cannon Instruments as part number 9728-V95.<br />
9.1.1.2.2 A wafer-shaped RTD shall be mounted between the plates and used as<br />
described in section 6.1.2.2. The RTD must be calibrated as described in note 5 to the<br />
nearest 0.1 °C. A suitable RTD is available from Omega as part number RTD FN105. This<br />
RTD is not waterproof and must be dipped in hot asphalt prior to calibration. To obtain<br />
measurements, the RTD is mounted in the rheometer within the asphalt binder sample. After<br />
mounting the sample and trimming excess asphalt binder, proceed with the temperature<br />
measurements as described in section 6.1.2.2.<br />
35
9.1.1.2.3 A thermocouple probe shall be used to measure the sample temperature by<br />
inserting the probe into a sample that has been mounted in the rheometer (this procedure is<br />
described in section 10). The thermocouple must be calibrated at 3 month intervals using the<br />
procedure described in note 5 to the nearest 0.1 °C. When obtaining the sample temperature<br />
the cabling and instrumentation must remain unchanged from that used during the calibration.<br />
To make a sample temperature reading insert the thermocouple in the asphalt binder between<br />
the plates and proceed as described in section 6.1.2.3. A suitable thermocouple probe is<br />
available from Omega as part number HYP1-30-1/2-T-G-60-SMP-M.<br />
9.1.2 Calibrate the load transducer in accordance with the directions and f'Lxtures<br />
supplied with the apparatus.<br />
9.1.3 Calibrate the strain transducer in accordance with the directions and fixtures<br />
supplied with the apparatus.<br />
9.1.4 Verify the overall calibration of the DSR using suitable reference fluids with<br />
viscoelastic properties similar to asphalt binder. Do not attempt to verify individual load or<br />
deflection detectors with a reference fluid. Suitable standards have not been identified.<br />
NOTE6.--Reference fluids exhibiting moduli and phase angles within the range of measurement may be<br />
used for verification purposes. Because reference fluids do not have the same temperature dependency as asphalt<br />
binder, caution must be used when interpreting the results obtained from such fluids.<br />
10. PREPARING SAMPLES AND TEST SPECIMENS<br />
10.1 Preparing Test Samples--If unaged binder is to be tested, obtain test samples<br />
according to T40.<br />
10.1.1 Anneal the asphalt binder from which the test specimen is to be obtained by<br />
heating until it is sufficiently fluid to pour the required specimens. Annealing prior to testing<br />
removes reversible molecular associations (steric hardening) that occur during normal storage<br />
at ambient temperature. Do not exceed a temperature of 163°C. Cover the sample and stir it<br />
occasionally during the heating process to ensure homogeneity and to remove air bubbles.<br />
Minimize the heating temperature and time to avoid hardening the sample.<br />
NoTE 7.--Minimum pouring temperatures that produce a consistency equivalent to that of SAE 10W30<br />
motor oil (readily pours but not overly fluid) at room temperature are recommended. Heating unaged asphalt to<br />
temperatures above 135°C should be avoided. With some modified asphalts or heavily aged binders, however,<br />
pouring temperatures above 135°C may be required.<br />
10.1.2 Cold material from storage containers must be annealed prior to usage.<br />
Structure developed during storage can result in overestimating the modulus by as much as<br />
50%.<br />
10.2 Preparing Test Specimens--Carefully clean and dry the surfaces of the test plates<br />
so that the specimen adheres to both plates uniformly and strongly. Bring the chamber to<br />
approximately 45 °C so that the plates are preheated prior to the mounting of the test<br />
36
specimen. This will provide sufficient heat so that the asphalt binder may be squeezed<br />
between the plates for trimming and to ensure that the asphalt binder adheres to the plates.<br />
Serrated plates or otherwise roughened plates are not necessary to ensure load transfer<br />
between the asphalt binder and the plates as long as the plates are clean and dry when the<br />
test specimen is prepared. Prepare a test specimen using one of the methods specified in<br />
sections 10.2.1 or 10.2.2.<br />
10.2.1 Alternate/--Remove the removable plate and, while holding the sample<br />
container approximately 15 mm above the test plate surface, pour the asphalt binder at the<br />
center of the upper test plate continuously until it covers the entire plate except for an<br />
approximate 2-mm-wide strip at the perimeter (note 8). Carefully insert the RTD. Wait<br />
several minutes for the specimen to stiffen, then mount the test plate in the rheometer for<br />
testing.<br />
NOTE8.--An<br />
eye dropper or syringe may be used to transfer the hot asphalt binder to the plate.<br />
10.2.2 Alternate 2--Pour the hot asphalt binder into a silicone rubber mold that will<br />
form a pellet that has a diameter approximately equal to the diameter of the upper test plate<br />
and a height approximately equal to 1.5 times the width of the test gap. Carefully insert the<br />
RTD. Allow the silicone rubber mold to cool to room temperature. Remove the specimen<br />
from the mold and center the pellet on the lower plate of the DSR.<br />
NOTE9.--The filled mold may be chilled in a freezer to facilitate demolding of softer grades of asphalt<br />
binder. Chill the mold in the freezer for only the minimum time needed to facilitate demolding the specimen.<br />
10.3 Test Specimen Trimming--After the specimen has been placed on one of the test<br />
plates as described above, move the test plates together to squeeze the asphalt mass between<br />
the two plates. Move the plates together until the gap between plates equals the testing gap<br />
plus 0.05 mm.<br />
10.3.1 Trim excess asphalt from the specimen by moving a heated trimming tool<br />
around the upper and lower plate perimeters. The tool may be heated on a hot plate or with a<br />
flame.<br />
NOTE 10.--The calculated modulus is proportional to the fourth power of the specimen radius. Carefully<br />
trim the specimen to insure that the measurements are reliable.<br />
10.3.2 When the trimming is completed, decrease the gap by 0.05 mm to the desired<br />
testing gap. This will cause a slight bulging of the asphalt binder at the periphery of the test<br />
specimen.<br />
11. PROCEDURE<br />
11.1 Bring the specimen to the test temperature + 0.1°C. See note 4.<br />
NOTE ll.--The gap should be set at the starting test temperature (section 11.1.1) or at the middle of the<br />
expected range of test temperatures (section 11.1.2). See sections 8.4 and 8.5 for guidance on setting the gap.<br />
37
Typically, reliable test results may be obtained with a single sample, in an 8-ram or 25-mm plate, using temperatures<br />
within 12°C of the temperature at which the gap is set.<br />
11.1.1 When testing a binder for compliance with MP1, select the appropriate test<br />
temperature from table 1 of MP1.<br />
11.1.2 When conducting a temperature sweep, start at a mid-range test temperature<br />
and increase or decrease the test temperature to cover the desired range of test temperatures.<br />
(See sections 6 and 7 in PP6.)<br />
11.2 Set the temperature controller to the desired test temperature, including any<br />
difference as required by section 9.1.1.2. Allow the temperature indicated by the RTD to<br />
come to the desired temperature. The test shall be started only after the temperature has<br />
remained at the desired temperature + 0.1 °C for at least 10 minutes. After temperature<br />
equilibration, anneal the specimen for 5 minutes.<br />
NOTE 12.--It is impossible to specify a single equilibration time that is valid for different manufacturers'<br />
DSRs. The design (fluid bath or air oven) of the environmental control system and the starting temperature will<br />
dictate the time required to reach the test temperature.<br />
11.3 Strain Control Mode--When operating in a strain controlled mode, determine<br />
the strain value according to the value of the complex modulus. Control the strain within<br />
20 % of the target value calculated by equation 1.<br />
where<br />
3' = shear strain in percent<br />
G* = complex modulus in kPa<br />
3, = 12.0/(G*) °'29 (1)<br />
11.3.1 When testing specimens for compliance with MP1, select an appropriate strain<br />
value from table 2. Software is available with the dynamic shear rheometers that will control<br />
the strain automatically.<br />
Table 2. Target Strain Values<br />
Material G* (kPa) Strain (%)<br />
Target Value<br />
Range<br />
Original Binder 1.0 12 9 to 15<br />
RTFO Residue 2.2 10 8 to 12<br />
PAV Residue 5.0 1 0.8 to 1.2<br />
11.4 Stress-Controlled Mode--When operating in a stress-controlled mode, determine<br />
the stress level according to the value of the complex modulus. Control the stress within 20 %<br />
of the target value calculated by equation 2.<br />
38
= 0.12(G*) °m (2)<br />
where<br />
r = shear stress in kPa<br />
G* = complex modulus in kPa<br />
11.4.1 When testing specimens for compliance with MP1, select an appropriate stress<br />
level from table 3. Software is available with the dynamic shear rheometers that will control<br />
the stress level automatically without control by the operator.<br />
Table 3. Target Stress Levels<br />
Stress (kPa)<br />
Material<br />
G* (kPa)<br />
Target Level<br />
Range<br />
Original Binder 1.0 0.12 0.09 to 0.15<br />
RTFO Residue 2.2 0.22 0.18 to 0.26<br />
PAV Residue 5.0 50.0 40 to 60<br />
11.5 When the temperature has equilibrated, condition the specimen by applying the<br />
required strain for 10 cycles at a frequency of 10 rad/s (note 13). Obtain test measurements<br />
by recording data for an additional 10 cycles. Reduce the data obtained for the second<br />
10 cycles to produce a value for the complex modulus and phase angle. Typically a Fast<br />
Fourier Transform (FFT) is used to reduce the data. The data acquisition system<br />
automatically acquires and reduces the data when properly activated. When conducting tests<br />
at more than one frequency, start testing at the lowest frequency and increase to the highest<br />
frequency.<br />
NOTE 13.--The<br />
standard frequency of 10 rad/s is used when testing binder for compliance with MP1.<br />
11.6 The data acquisition system specified in section 6.1.4 automatically calculates<br />
G* and 6 from test data acquired when properly activated.<br />
11.7 Initiate the testing immediately after preparing and trimming the specimen.<br />
The testing at subsequent temperatures should be done as quickly as possible to minimize the<br />
effect of molecular associations (steric hardening) that can cause an increase in modulus if<br />
the specimen is held in the rheometer for a prolonged period of time. When testing at<br />
multiple temperatures, all testing should be completed within 4 hours.<br />
12. INTERPRETATION OF RESULTS<br />
12.1 The dynamic modulus and phase angle depend upon the magnitude of the shear<br />
strain; the modulus and phase angle for both unmodified and modified asphalt cement<br />
decrease with increasing shear strain as shown in figure 1. A plot such as that shown in<br />
39
figure 1 can be generated by gradually increasing the load or strain amplitude, thereby<br />
producing a strain sweep. It is not necessary to generate such sweeps during normal<br />
specification testing; however, such plots are useful for verifying the limits of the linear<br />
region.<br />
12.2 A linear region may be defined at small strains where the modulus is relatively<br />
independent of shear strain. This region will vary with the magnitude of the complex<br />
modulus. The linear region is defined as the range in strains where the complex modulus is<br />
95 % or more of the zero-strain value.<br />
12.3 The shear stress varies linearly from zero at the center of the plates to a<br />
maximum at the extremities of the plate perimeter. The shear stress is calculated from the<br />
applied or measured torque, measured or applied strain, and the geometry of the test<br />
specimen.<br />
13. REPORT<br />
13.1 Provide a complete identification and description of the material tested including<br />
name code, source, and type of sample container.<br />
13.2 Describe the instrument used for the test. Include the model number, whether it<br />
is a constant strain or constant stress rheometer, the type of environmental chamber, and<br />
other information needed to describe the rheometer.<br />
13.3 The strain and stress levels specified in tables 2 and 3 have been selected to<br />
ensure a common reference point that has been shown to be within the linear region for plain<br />
and modified asphalt binders. Some systems may not be linear within this region. When this<br />
situation is observed, report the modulus at the recommended stress or strain levels but<br />
report that the test conditions were outside the linear region.<br />
13.4 For each test, report the following:<br />
13.4.1 the test plate diameter, to the nearest 0.1 mm;<br />
13.4.2 the test gap, to the nearest l#m;<br />
13.4.3 the test temperature, to the nearest 0.1°C;<br />
13.4.4 the test frequency, to the nearest 0.1 rad/s;<br />
mN.m,<br />
13.4.5 the strain amplitude, to the nearest 0.01%, or the torque, to the nearest<br />
13.4.6 the complex modulus (G*) for the ten measurements, in kPa to three<br />
significant figures; and<br />
4O
13.4.6 the phase angle (iS)for the second ten cycles, to the nearest 0.1 degrees.<br />
14. PRECISION AND BIAS<br />
14.1 Precision--The research required to develop estimates of precision has not<br />
been conducted.<br />
14.2 Bias--The research required to establish the bias of this method has not been<br />
conducted.<br />
15. KEY WORDS<br />
Asphalt binder, complex modulus, dynamic shear rheometer.<br />
41
150<br />
"ZERO" STRAIN<br />
VALUE<br />
O" STRAIN VALUE<br />
•_ 100<br />
0<br />
if) 5O<br />
0<br />
0 tO 20 30<br />
Shear Strain,<br />
percent<br />
Figure 1. Example of a Strain Sweep Test Used to Define the Linear Viscoelastic<br />
for Dynamic Mechanical Testing of Asphalt<br />
Limit<br />
42
Standard Method of Test for<br />
Determining the Fracture Properties of<br />
Asphalt Binder in Direct Tension<br />
AASHTO Designation: TP3 _<br />
1. SCOPE<br />
1.1 This test method covers the determination of the failure strain and failure stress<br />
of asphalt binders by means of a direct tension test. It is applicable to material that has a<br />
failure strain less than 10% and can be used with unaged material or with material aged<br />
using T240 (RTFOT), T179 (TFOT), or PP1 (PAV). The test apparatus is designed for<br />
testing within the temperature range from -40°C to 25°C.<br />
1.2 This test method is limited to asphalt binders that contain particulate material less<br />
than 250/_m in diameter.<br />
1.3 This test method is not valid for specimens that exhibit a strain to failure outside<br />
the defined brittle-ductile range (_> 10%).<br />
1.4 The values stated in SI units are to be regarded as the standard.<br />
1.5 This standard may involve hazardous materials, operations, and equipment. This<br />
standard does not purport to address all of the safety problems associated with its use. It is<br />
the responsibility of the user of this procedure to establish appropriate safety and health<br />
practices and to determine the applicability of regulatory limitations prior to use.<br />
2. REFERENCE DOCUMENTS<br />
2.1 AASHTO Standards:<br />
MP1 Specification for Performance-Graded Asphalt Binder<br />
PP1 Practice for Accelerated Oxidative Aging of Asphalt Binder<br />
Using a Pressurized Aging Vessel<br />
T40 Practice for Sampling Bituminous Materials<br />
1Thisstandardis basedon <strong>SHRP</strong>Product1005.<br />
43
T179 Test Method for Effect of Heat and Air on Asphalt Materials (Thin-Film Oven<br />
Test)<br />
T240<br />
Test Method for Effect of Heat and Air on Rolling Film of<br />
Asphalt (Rolling Thin-Film Oven Test)<br />
2.2 ASTM Standards:<br />
E1 Specification for ASTM Thermometers<br />
E4 Practice for Load Verification of Testing Machines<br />
E83 Method of Verification and Classification of Extensometers<br />
E220 Method for Calibration of Thermocouples by Comparison Techniques<br />
2.3 DIN Standards<br />
43760<br />
2.4 MIL Standards<br />
5545<br />
45662<br />
45662A<br />
3. TERMINOLOGY<br />
3.1 Definitions<br />
3.1.1 asphalt binder, n--an asphalt-based cement that is produced from petroleum<br />
residue either with or without the addition of non-particulate organic modifiers.<br />
3.2 Description of Terms Specific to This Standard<br />
3.2.1 brittle, adj--refers to a type of failure in a direct tension test where the stressstrain<br />
curve is essentially linear up to the point of failure and the failure is by sudden rupture<br />
of the test specimen without appreciable reduction in the cross section of the specimen.<br />
3.2.2 brittle-ductile, adj--refers to type of failure in a direct tension test where the<br />
stress-strain curve is curvilinear and the failure is by sudden rupture of the test specimen. A<br />
limited reduction in the cross section of the specimen occurs before rupture.<br />
3.2.3 ductile, adj--refers to a type of failure in a direct tension test where the<br />
specimen does not rupture but fails by flow at large strains.<br />
44
3.2.4 engineering strain, n--refers to the axial strain resulting from the application of<br />
a tensile load and calculated as the change in length caused by the application of the tensile<br />
load divided by the original unloaded length of the specimen without any correction for<br />
reduction in its cross section.<br />
3.2.5 failure, n--refers to the point at which the tensile load reaches a maximum<br />
value as the test specimen is pulled at a constant rate of elongation.<br />
3.2.6 failure stress, n--the tensile stress on the test specimen when the load reaches a<br />
maximum value during the test method specified in this standard.<br />
3.2.7 failure strain, n--the tensile strain corresponding to the failure stress.<br />
4. SUMMARY OF TEST METHOD<br />
4.1 This method describes the procedure used to measure the strain at failure and<br />
stress at failure in an asphalt binder test specimen pulled at a constant rate of elongation.<br />
Test specimens are prepared by pouring hot asphalt binder into a suitable mold. Two plastic<br />
inserts are used to grip the asphalt binder during the test and to transfer the tensile load from<br />
the test machine to the test specimen.<br />
4.2 This test procedure was developed for asphalt binders at temperatures where they<br />
exhibit brittle or brittle-ductile failure. A brittle or brittle-ductile failure will result in a<br />
fracture of the test specimen as opposed to a ductile failure in which the specimen simply<br />
stretches without fracturing. The test is not applicable at temperatures where failure is by<br />
ductile flow.<br />
4.3 A non-contact extensometer is used to measure the elongation of the test<br />
specimen as it is pulled in tension at a constant rate of elongation of 1 mm/min. The<br />
maximum load developed during the test is monitored. The tensile strain and stress in the test<br />
specimen when the load reaches a maximum is reported as the failure strain and failure<br />
stress, respectively.<br />
5. SIGNIFICANCE AND USE<br />
5.1 The strain at failure is a measure of the amount of elongation that an asphalt<br />
binder can sustain without cracking. Strain at failure is used as a criterion for specifying the<br />
low-temperature properties of asphalt binder in accordance with MP1.<br />
5.2 The test is designed to identify the temperature region where the asphalt binder<br />
has limited ability to elongate without cracking. In the asphalt binder specification, a lower<br />
limit is placed on the allowable strain to failure at a specified temperature and rate of<br />
elongation.<br />
45
5.3 For evaluating an asphalt binder for conformance to MP1, the elongation rate is<br />
1.0 mm/min and the test temperature is selected from table 1 of MP1 according to the grade<br />
of asphalt binder. Other rates of elongation and test temperatures may be used to test asphalt<br />
binders.<br />
6. APPARATUS<br />
6.1 Direct Tension Test System--A direct tension test system consisting of (1) a<br />
displacement-controlled tensile loading machine, (2) a specimen gripping system, (3) a<br />
chamber for environmental conditioning and testing, (4) load measuring and recording<br />
devices, (5) elongation measuring and recording devices, (6) a temperature detection device,<br />
and (7) data acquisition and display devices.<br />
6.1.1 Tensile Loading Machine--A tensile loading machine with a controlleddisplacement<br />
loading frame capable of producing at least a 500 N load is required.<br />
The platen movement shall be controlled with either one or two motor-driven screws or<br />
with a hydraulic-controlled actuator. Screw-type loading frames are typically used for<br />
this test, although a hydraulic closed-loop testing frame is acceptable if the requirements<br />
specified in this standard are met. The loading frame shall produce a crosshead speed of<br />
1.00 _ 0.05 mm/min. Additional crosshead speeds may be supplied but are not required.<br />
The testing frame shall be equipped with an automatic return feature that returns the crosshead<br />
to a reference position such that the center-to-center spacing of the loading pins is<br />
100.0 mm + 0.1 mm. The testing frame shall be equipped with two standards with sufficient<br />
clear space between the standards so that an environmentally controlled chamber with<br />
dimensions given in section 6.1.3 can be placed between the standards.<br />
6.1.2 Specimen Gripping System--The gripping system shall produce a self-aligning<br />
uniaxial test load, accept the plastic end units described in section 6.1.2.1 and be designed so<br />
that test specimens can be easily mounted in the machine. The system shall include two<br />
grips. Each grip shall include a specially-shaped pin that is mounted rigidly to the upper and<br />
lower platens of the testing machine. Figure 1 specifies the dimensions of the top and bottom<br />
grips. One grip shall be fixed and remain stationary during the test while the other grip is<br />
displaced at the desired rate. Figure 2 specifies the dimensions of the loading pins used with<br />
the grips.<br />
6.1.2.1 Specimen Plastic End Inserts--PMMA (Plexiglas ®) end inserts having the<br />
dimensions specified in figure 3 shall be used on both ends of the test specimen to transfer<br />
the tensile load to the asphalt binder. Each end insert contains a precisely machined hole and<br />
slot. The diameter of the hole is slightly larger than the diameter of the pin. The slots on the<br />
top and bottom inserts allow two spots of laser light to pass the test specimen and shine upon<br />
the receiver. Gripping of the specimen is accomplished through the bond (adhesion) between<br />
the asphalt binder test specimen and the plastic end insert. Each end insert mounts on a<br />
specially shaped pin that is part of the gripping system. The specimen is attached to the top<br />
and bottom grips by positioning the end inserts in the test machine such that the plastic<br />
inserts fit onto the pins and are indexed against the face of the grips. Matching the coefficient<br />
46
of thermal expansion of the asphalt binder and the inserts is necessary to reduce thermal<br />
shrinkage stresses at the interface that otherwise cause bond failures.<br />
NOTE1.--PMMA (Plexiglas®), meeting MIL STD-5545, has been found acceptable for making the inserts.<br />
It is readily available, opaque to the laser beam, has a satisfactory coefficient of thermal expansion, and is easy to<br />
machine.<br />
6.1.3 Environmental Conditioning and Testing Chamber--The environmental<br />
conditioning and testing chamber shall be capable of controlling temperature and humidity<br />
and performing isothermal conditioning of test specimens prior to testing. It should be on the<br />
order of 300 mm wide by 200 mm deep by 450 mm high and shall completely enclose the<br />
specimen and gripping system. It shall be capable of controlling test temperatures between<br />
-40°C and ambient with variations within the chamber _< 0.2°C. It shall be equipped with<br />
a cooling system that has the capacity to reduce the chamber temperature from ambient to<br />
-40°C within 40 minutes and to change the chamber temperature from -30 to -40°C or<br />
from -40 to -30°C within 10 minutes. Mechanical cooling or liquid nitrogen may be used<br />
to cool the chamber. It shall have a dehumidifying system with a capacity such that the<br />
formation of frost on the interior of the chamber, the test specimen, or any of the test<br />
fixtures is eliminated.<br />
6.1.3.1 The chamber shall be capable of storing a minimum of 16 test specimens on<br />
a rack which is thermally isolated from the walls and floors of the chamber such that heat<br />
conducted from the walls and floors of the chamber does not affect the temperature of the<br />
stored specimens.<br />
NOTE2.--A demolded test specimen is placed on Plexiglas ®, Teflon ®or other plastic plate (with<br />
approximate dimensions of 6 mm thick by 20 mm wide by 100 mm long) and transferred to the environmentally<br />
controlled test chamber for thermal conditioning. The use of a transfer plate will minimize deformation during<br />
handling. Each plate, when the above dimensions are used, accommodates up to four demolded test specimens.<br />
6.1.3.2 The chamber shall be fitted with a front-opening door for maintenance and<br />
standardization purposes and an access port that allows for insertion of the operator's hand<br />
and forearm to position test specimens on the storage shelf for conditioning and to position<br />
test specimens on the grips for testing. The access port shall be designed so that changes in<br />
chamber temperature are < 0.2°C during an operation in which the operator's hand or<br />
forearm is inserted into or removed from the chamber. Visual access to the interior of the<br />
test chamber shall be provided to permit proper mounting of test specimens and test<br />
monitoring. The test specimen elongation is measured with an optical laser. Use of the laser<br />
requires optical glass windows on two sides of the temperature chamber so that a beam of<br />
laser light can be passed through the chamber without distorting the beam.<br />
6.1.4 Load Measuring and Recording Devices--Load shall be measured with a load<br />
cell having a minimum capacity of 500 N and a sensitivity of 0.1 N. The load cell shall be<br />
calibrated at least annually in accordance with ASTM E4. The load and elongation shall be<br />
monitored with the data acquisition system such that they can be resolved to 1% of the<br />
failure load and elongation, respectively. Once the test has started, the data acquisition<br />
system shall be able to detect the point in time when the load starts to change as a result of<br />
elongation in the sample. This shall be accomplished by monitoring the load cell signal with<br />
47
time. A change in the load signal equivalent to 1 to 2 N (threshold load) shall be used to<br />
mark the point in time where zero reading of the extensometer is obtained. The point in time<br />
where the peak load is obtained will be captured by the data acquisition system and the<br />
accumulated elongation from the zero reading to the elongation corresponding to the peak<br />
load shall be used to calculate the failure strain. Once the test is complete, the device shall<br />
display the strain at failure. Peak load typically ranges from 10 to 100 N depending on the<br />
test temperature, grade, aging, and source of the binder. Stress and strain shall be displayed<br />
to the nearest 0.1 N.<br />
6.1.5 Elongation Measuring and Recording Devices--Specimen elongation shall be<br />
measured with a laser light transmitter and receiver. The non-contact laser extensometer shall<br />
be calibrated at least annually according to ASTM E83, MIL-STD 45662 and MIL-STD<br />
45662A. The transmitter shall produce a vertical plane of laser light that is monitored by the<br />
receiver and shall be arranged so that the test specimen interrupts the plane of laser light<br />
except for the slots in the insert. Thus, two spots of laser light are transmitted to the<br />
receiver. The receiver shall constantly monitor the relative position of the two spots of laser<br />
light to produce a voltage proportional to the distance between the two nearest edges of the<br />
spots of light. This voltage shall be converted to elongation by a controller attached to the<br />
receiver using a calibration factor determined by the manufacturer and verified when the<br />
extensometer is calibrated. The laser measurement range shall be 30 to 60 mm with an<br />
accuracy _< 0.005 mm. Elongations shall be recorded to the nearest 0.005 ram.<br />
6.1.6 Temperature Detection Device--The temperature detection device shall be a<br />
calibrated resistance thermal detector (RTD) readable and accurate to 0.1°C (note 3). The<br />
RTD shall be mounted inside the environmental chamber in the immediate vicinity of the test<br />
specimen. Cabling to the RTD shall be of sufficient length that the bulb of a total immersion<br />
mercury-in-glass thermometer can be held adjacent to the RTD for standardization purposes<br />
(See section 9.1.3).<br />
NOTE3.--Required temperature measurement can be accomplished with an appropriately calibrated<br />
platinum resistance thermometer (RTD) or thermistor. Platinum resistance thermometers meeting DIN Standard<br />
43760 (Class A) are recommended for this purpose. The required precision and accuracy cannot be obtained unless<br />
each RTD or thermistor is calibrated as a system with its respective meter or electronic circuitry (See section 9.1.3).<br />
6.1.7 Data Acquisition and Display Device--The data acquisition and display device<br />
shall display the load and elongation selected by the operator (stress and strain) on an LED<br />
(or other appropriate computer controlled display) during the time the test specimen is<br />
loaded. It shall detect the peak load and capture the elongation associated with the peak load.<br />
The maximum skew time between the load and corresponding elongation shall be 0.015 s.<br />
6.1.7.1 The data acquisition component shall consist of an IBM-compatible computer<br />
with three A/D channels; one for load (the load cell), one for elongation (the laser), and one<br />
for temperature (the RTD). Data shall be stored in ASCII format.<br />
6.1.7.2 Display of Stress-Strain Curve--The data acquisition and display system shall<br />
be capable of displaying a stress-strain curve in units of stress (MPa) versus strain (percent).<br />
This may be accomplished using the video screen of the data acquisition computer or with an<br />
48
x-y recorder. If a recorder is used, the units may be recored in volts but the test file shall<br />
contain the calibration factor in megapascals/volt and percent strain/volt for both the x and y<br />
axes.<br />
6.2 Specimen Molds--The specimen molds shall be manufactured from silicone<br />
rubber available from Dow Coming (HSII RTV Moldmaking Rubber 20:1 Kit, white in<br />
color). Silicone rubber is used because it is dimensionally stable, provides an excellent nonstick<br />
surface for asphalt binder, and is easy to clean. Specimens and molds shall have the<br />
dimensions specified in figures 4 (silicone rubber molds) and 5 (aluminum molds).<br />
6.3 Specimen Mold Support Plates--Aluminum plates 5 to 10 mm thick to support<br />
the rubber molds when molding test specimens are required.<br />
6.4 Specimen Storage Plates--Plexiglas, Teflon, or other plastic plates for<br />
transferring and storing test specimens in the environmental chamber.<br />
6.5 Calibrated thermometer--A calibrated liquid-in-glass thermometer of suitable<br />
range with subdivisions of 0.1°C is required for verification of the temperature transducer.<br />
This thermometer shall be calibrated in accordance with ASTM E77. An ASTM 62C<br />
thermometer is suitable.<br />
6.6 Load Verification Equipment--Known dead masses (traceable to NIST) ranging<br />
10 to 500 4-0.1 N (1 to 50 + 0.1 kg) are required for verifying the calibration of the load<br />
cell.<br />
7. MATERIALS<br />
7.1 Solvent (Varsol or mineral spirits) or a degreasing spray cleaner formulated for<br />
use on plastic for cleaning molds, plastic end inserts and aluminum plates<br />
7.2 Cleaning cloths (cotton) for wiping molds, end inserts and plates<br />
8. HAZARDS--Use the standard laboratory safety procedures required for handling the hot<br />
asphalt binder when preparing test specimens and the required safety procedures when<br />
cleaning with solvents or degreasers.<br />
9. CALIBRATION AND STANDARDIZATION<br />
9.1 Verify calibration of the extensiometer, load cell, and temperature transducer.<br />
NOTE4.--Calibration is usually performed by a calibration service agency. Calibration verification, system<br />
standardization, and quality checks may be performed by the manufacturer, other agencies providing such services,<br />
or in-house personnel using the procedures described below.<br />
49
9.1.1 Load cell--Verify calibration of the load cell at least every 6 months using<br />
dead masses suspended from the load cell.<br />
9.1.2 Non-Contact Extensometer--Verify calibration of the non-contact extensometer<br />
at least every month using the fixture shown in figure 6. Place the fixture in the test machine<br />
and apply a 20 to 50 N load on the fixture to hold the fixture firmly in the grips. Insert the<br />
gauge in the fixture and measure the short dimension of the gauge with the laser. Remove<br />
the gauge from the fixture and measure the long dimension. Check the length of the gauge as<br />
measured with a similar reference measurement made on the gauge during the last<br />
calibration. If the verification measurement and the reference measurement differ by more<br />
than 0.006 mm, either calibration or maintenance is required.<br />
equilibrium.<br />
NOTE5.--Measurements should be made at -120C. Allow sufficient time for gauge to achieve thermal<br />
9.1.3 Temperature Detector--Verify calibration of the temperature detector at least<br />
every six months by comparing the output of the RTD with a calibrated mercury-in-glass<br />
thermometer in accordance with ASTM E220. Place the thermometer in the environmentally<br />
controlled chamber. Hold the RTD in intimate contact with the bulb of the thermometer with<br />
a rubber O-ring or other suitable technique. When the thermometer and the temperature<br />
detection device have reached equilibrium, compare the temperature indicated on the<br />
detector's readout to the temperature indictated on the thermometer by reading through the<br />
observation port on the door of the chamber. If the temperature indicated by the thermal<br />
detector does not agree with the mercury-in-glass thermometer 4- 0.1°C, further calibration<br />
or maintenance is required.<br />
9.1.4 Verify the speed of the crosshead by using a dial gauge and a stopwatch.<br />
Mount a dial gauge on a fixed portion of the testing machine in a manner such that the stem<br />
of the dial gauge senses the movement of the crosshead. Be careful to ensure that the<br />
movement of the stem of the dial gauge is parallel to the movement of the crosshead and that<br />
the dial gauge is firmly attached to the Votedportion of the testing machine. Mounting the<br />
dial gauge on a magnetic base is a convenient method for attaching the dial gauge to the<br />
testing machine. Select the desired crosshead speed and start operating the machine at the<br />
desired speed. As the machine is running, start the stopwatch and simultaneously obtain an<br />
initial reading of the dial gauge. Approximately one minute later, obtain a second reading<br />
and simultaneously stop the stopwatch. Calculate the speed of the crosshead by dividing the<br />
difference between the initial and final dial gauge reading in millimeters by the stopwatch<br />
time in minutes.<br />
10. PREPARATION OF SAMPLES AND TEST SPECIMENS<br />
10.1 Preparing Test Samples--If unaged binder is to be tested, obtain test samples<br />
according to T40.<br />
5O
10.2 Anneal the asphalt binder for the test specimen by heating until it is sufficiently<br />
fluid to pour. Annealing prior to testing removes reversible molecular associations (steric<br />
hardening) that occur during normal storage at ambient temperature.<br />
NOTE6.--Minimum pouring temperatures that produce a consistency equivalent to that of SAE 10W30<br />
motor oil (readily pours but not overly fluid) at room temperature are recommended. The specific temperature will<br />
depend on the grade of binder and its prior aging history, if any. Temperatures less than 135°C are desirable.<br />
Temperatures above 135°C may be required, however, for some modified asphalt binders or heavily aged binders.<br />
10.3 Place the plastic end inserts into both ends of the mold. Place the molds and<br />
inserts into a 163°C oven for 30 minutes.<br />
10.4 After heating, place the mold on a 6- to 7-mm-thick aluminum plate. Do not<br />
preheat the aluminum plate. Pour hot asphalt binder into the mold by starting at one end of<br />
the mold and moving across the mold in a single pass. Pour the specimen in a continuous<br />
stream to avoid entraining air bubbles or gaps. Complete the pouring operation as quickly as<br />
possible to avoid any excessive drop in the temperature of the asphalt binder. Stop pouring<br />
when the asphalt is slightly above the top surface of the mold.<br />
10.5 After pouring the test specimen, allow the entire assembly to cool on the<br />
benchtop at ambient temperature for approximately one hour. Do not quench the specimen to<br />
achieve ambient temperature.<br />
10.6 As soon as the specimen has cooled to room temperature, trim off the excess<br />
asphalt binder with a straight cutting edge (e.g., a flat cheese cutter or spatula) so that the<br />
asphalt binder is flush with the top of the mold. Use care during the trimming operation so<br />
that the asphalt binder is not pulled away from the mold and that the bond between the<br />
plastic inserts and the asphalt binder is not damaged. Trim the specimen in a consistent<br />
manner. Pull the cutting edge along the long axis of the sample flush with the surface of the<br />
mold to remove the excess asphalt binder. After trimming, remove all debris or extraneous<br />
asphalt binder from the holes or slots in the plastic insert.<br />
NOTE7.--Caution:<br />
occurs, discard the sample.<br />
Excessive downward pressure during trimming will distort the sample mold. If this<br />
10.7 Immediately prior to demolding, place the mold containing the specimen in a<br />
freezer at -5 + 5 °C until the specimen is sufficiently stiff to demold without distorting the<br />
sample. Some softer grades may require lower temperatures. Time in the freezer should not<br />
exceed 15 minutes. After demolding, place the sample on the specimen storage plate (see<br />
section 6.4). Measurement of specimen dimensions after demolding is not necessary since<br />
dimensional tolerances are closely controlled in the molding process.<br />
11. PROCEDURE<br />
11.1 Set the environmental chamber at the desired testing temperature and wait until it<br />
stabilizes to within + 0.2°C-of the desired test temperature. When testing for compliance<br />
with MP1, use the test temperatures specified in table 1 of MP1.<br />
51
11.2 Immediately after demolding, place the test specimens in the chamber on the<br />
plastic storage plate and condition the specimens at the test temperature for 1 hour + 10<br />
minutes. Adhere carefully to time schedule to avoid testing variability that is caused by<br />
physical hardening.<br />
11.3 After 1 hour ± 10 minutes, mount the specimen on the pins using the<br />
environmental chamber hand access port, centering the back face of the insert on the<br />
mounting pin. Do not open the chamber door to handle or mount the specimen because that<br />
will produce excessive temperature fluctuations that will take time to stabilize and lead to<br />
variable thermal histories. Handle the specimens with latex surgical gloves to protect the<br />
operator's fingers and to minimize heating of the specimen. Handle the specimen by touching<br />
only the plastic inserts--do not touch the asphalt binder.<br />
NOTE8.--Air currents from the circulation fan may cause the inserts to move after being placed on the<br />
mounting pins. A silicone rubber or foam washer that remains flexible at the test temperature will help to hold the<br />
insert against the face of the grip. It is important that the insert be centered on the pin (flush against the face of the<br />
grip) in order for the load to be applied axially through the center of the test specimen. A suitable washer may be cut<br />
from silicone rubber or foam sheeting with a cork borer. The washer may be 5-10 mm thick with an outer diameter<br />
of approximately I0 mm. The inside diameter of the washer shall be sufficient to provide a friction fit on the 5-mm<br />
portion of the pin. The washer should slide easily on the pin providing only sufficient force to hold the insert in<br />
place during the test.<br />
11.4 Select the desired deformation rate and load the specimen to failure. Select a<br />
deformation rate of 1.00 ± 0.05 mm/min when testing for compliance with MP1. If a test<br />
specimen fails outside the gauge area of the specimen (from throat to throat), discard the<br />
test.<br />
11.5 Alternate loading procedure--Apply a preload to the test specimen by mounting<br />
the specimen as previously described and applying an elongation sufficient to develop a 10 to<br />
20 N load; this may reduce testing variability. As soon as the 10 to 20 N load is reached,<br />
stop the movement of the platen and allow the load to relax until it is no longer detectable.<br />
The time required to relax the load will depend on the stiffness of the test specimen. Once<br />
the load has relaxed, continue the test as described in section 11.4.<br />
11.6 The strain at failure is easily identified as the strain at peak load (maximum<br />
stress) when the failure is by fracture (i.e., the specimen breaks into two pieces). However,<br />
if the specimen does not fracture but reaches a maximum stress and then flows without<br />
fracture, the strain at failure is recorded as the strain corresponding to the maximum stress.<br />
In some cases, the maximum stress may occur at strains greater than 10%. In this case, do<br />
not continue the test beyond 10% strain. Simply record the failure stress as "greater than<br />
10%." If the asphalt binder can be stretched to 10% without fracture, it meets the<br />
requirements of MP1 at the test temperature.<br />
11.7 If the plastic specimen end inserts are to be reused, break them off the asphalt<br />
binder while the asphalt binder is still cold. Discard the asphalt binder and clean the end<br />
inserts by soaking them in solvent and wiping with a soft cloth. Do not use acetone, TCE, or<br />
toluene, since such solvents will dissolve the plastic inserts. After wiping the inserts, use a<br />
detergent solution to remove oil film residue left by the mineral spirit cleaner. Alternatively,<br />
52
use a degreasing spray cleaner formulated for use on plastic. Clean the plastic inserts<br />
thoroughly. Grease on the asphalt bonding area can reduce bonding and cause bond failures.<br />
12. CALCULATION<br />
12.1 Compute the failure stress by dividing the failure load by the original area of<br />
the test specimen cross section as shown in equation 1:<br />
where<br />
Of = Pf/A (1)<br />
of = failure stress, MPa<br />
Pf = failure load, N<br />
A = original area of cross section, mm2<br />
NOTE 9.--For<br />
specimens used in this test, A = 3.6 mm_.<br />
12.2 Compute the failure strain by dividing the elongation at failure by the original<br />
gauge length, as shown in equation 2:<br />
where<br />
E:= (2)<br />
e/= failure strain, mm/mm<br />
6y = elongation at failure, mm<br />
L = gauge length, mm<br />
NOTE 10.--For specimens used in this test, the effective gauge length, L, is assumed to be 27.0 ram. This<br />
is an effective gauge length that represents the portion of the specimen that contributes to the majority of the strain.<br />
Strain values determined in this test may vary slightly from the actual strain at the point of fracture because of the<br />
assumed value for the gauge length.<br />
13. REPORT<br />
13.1 Report the following information:<br />
13.1.1 the sample identification;<br />
13.1.2 the date and time of test;<br />
13.1.3 the test temperature, to the nearest 0.1°C;<br />
13.1.4 the average rate of elongation, to the nearest 0.01 mm/min.;<br />
53
13.1.5 the average failure strain, to the nearest 0.01%;<br />
NOTE 11.--Direct tension testing of multiple specimens may produce obvious outliers. Until a statistically<br />
valid procedure is developed for considering outliers, discard any strain at failure values that are obvious outliers.<br />
13.1.6 the average failure stress, to the nearest 0.01 MPa;<br />
13.1.7 the average peak load, to the nearest N; and<br />
13.1.8 the type of fracture observed (fracture or no fracture).<br />
14. PRECISION AND BIAS<br />
14.1 Precision--The research required to develop precision estimates for this test<br />
method has not been conducted.<br />
14.2 Bias--The research required to establish the bias of this method has not been<br />
conducted.<br />
15. KEY WORDS<br />
Asphalt binder, direct tension, failure, failure strain, fracture, thermal cracking.<br />
54
I 26.0<br />
i_<br />
vI<br />
_o.o-_<br />
,. r_O_O .,-0.0_ _ 15.o<br />
'_ -- _/_.00 __.0.02 : /--9.5alia.<br />
'_ 5. _ 1<br />
/ ._ F,LLETOK<br />
_R =' 3.00 --. 0.02 mm<br />
12"0 "z-2O ............. _ O; _ *_r_ 15<br />
45<br />
75<br />
_<br />
Notes:<br />
!_ - • All dimensions in millimeters<br />
• Not to scale<br />
• Top and bottom assemblies are identical. Two<br />
assemblies are required.<br />
• Unless otherwise indicated, assume a<br />
tolerance of + 0.05 mm<br />
Figure 1. Top and Bottom Grip and Loading Pin Assembly<br />
55
IA<br />
A<br />
5,0 I<br />
6 0 86,0<br />
9,5<br />
FILLET O,K.<br />
/<br />
i0.0<br />
All dimensions<br />
Not to scale<br />
in millimeters<br />
_-- 5,0--_<br />
Figure 2. Loading Pins Used to Mount the Direct Tension Specimen<br />
56
..... l<br />
..... 10.0 dia. _I'_ 30.0<br />
-----_ 2.5rad. __ _,<br />
-,., Asphalt<br />
Section<br />
_Y<br />
J \<br />
_: End,._ _<br />
25.0 ,_ Insert " 30.0<br />
!o.o ! . o.o<br />
10.0 _ _,<br />
Notes:<br />
• All dimensions in millimeters<br />
• Not to scale<br />
• Unless otherwise indicated, assume a<br />
tolerance of + 0.05 mm<br />
Figure 3. Plastic End Inserts<br />
57
--__6_-<br />
-_A<br />
AL<br />
AL<br />
_<br />
o<br />
0<br />
_ _ _ "_ f-- 0" Y f<br />
d<br />
r=12 0<br />
--I_S 4_ ,-<br />
_- -4,<br />
B , B<br />
J \ ) \ / \_ .) \<br />
i.L<br />
2r_ _r<br />
$,,o I_1 ;,_.o<br />
1 •<br />
1 97.0<br />
'qr<br />
d<br />
15.0 20.0 25.0<br />
I<br />
-_<br />
SectionB- B<br />
T<br />
'°-°<br />
100.0 ,.]15"01_, i..<br />
,_.o,. .,oo, ;_--o-<br />
• Material: silicone<br />
15 I I I T rubber<br />
142.0 ._ • All millimeters dimensions in<br />
SectionA - A Not to scale<br />
• Tolerance + 0.03 mm<br />
Figure 4. Direct Tension<br />
Specimen Mold<br />
58
]<br />
15.0<br />
B<br />
14_.0<br />
40 100.0<br />
J<br />
B<br />
I'*-'- 20.0 4 15.0<br />
L_<br />
L 197.0<br />
DIRECT TENSION TYPE I MOLD<br />
I-'_°1<br />
I--_°°-I -_° l i _.o1 --1_,o<br />
p ,,,,, ,,,, ,,,, ,,,,, rl]o<br />
197.0<br />
SECTION B-B<br />
-,_o- L<br />
Avu,v<br />
,oo •: ""_°'1 "I I"-''° /<br />
SECTION A-A B1-CO No.: 1992-12<br />
Material: aluminum<br />
All dimensions in<br />
millimeters<br />
Tolerance: + 0.03 mm<br />
Figure 5.<br />
Specimen Mold Dimensions<br />
59
I<br />
__;___<br />
i<br />
--_'-- :" (_ . /_/Spring _1 Clip<br />
i.<br />
- _::<br />
'i<br />
-i-- - _'_--' _-<br />
3_3 Spring Clip : 20 _ Gauge<br />
Fixture<br />
---- * All dimensions in<br />
_ --_ 5 _- millimeters<br />
2.5 • Not to scale<br />
• Unless otherwise indicated,<br />
assume a tolerance of<br />
+ 0.05 mm<br />
Figure 6. Extensometer Verification Device<br />
6O
Standard Practice for<br />
Accelerated Aging of Asphalt Binder<br />
Using a Pressurized Aging Vessel<br />
AASHTO Designation: PP11<br />
1. SCOPE<br />
1.1 This practice covers the accelerated aging (oxidation) of asphalt binders by<br />
means of pressurized air and elevated temperature in a pressurized aging vessel (PAV). The<br />
test method is intended to simulate in-service oxidative aging of asphalt binders and is<br />
intended for use with residue from T240 (Rolling Thin Film Oven Test (RTFOT)) or T179<br />
(Thin Film Oven Test (TFOT)).<br />
NOTE1.--T240is the recommendedprocedure.Modifiedasphaltbindersmayphaseseparateor formskins<br />
duringconditioningwithT179(TFOT);the resultsfromsubsequent testingof thisresiduein TP5,TP1,andTP3<br />
maybe distorted.<br />
1.2 The aging of asphalt binders during service is affected by mixture-associated<br />
variables such as the volumetric proportions of the mix, the permeability of the mix,<br />
properties of the aggregates, and possibly other factors. This test is intended to provide an<br />
evaluation of the relative resistance of different asphalt binders to oxidative aging at selected<br />
temperatures and cannot account for mixture variables.<br />
1.3 The values stated in SI units are to be regarded as the standard.<br />
1.4 This standard may involve hazardous materials, operations, and equipment. This<br />
standard does not purport to address all of the safety problems associated with its use. It is<br />
the responsibility of the user of this procedure to establish appropriate safety and health<br />
practices and to determine the applicability of regulatory limitations prior to use.<br />
2. REFERENCE DOCUMENTS<br />
2.1 AASHTO Standards:<br />
M231 Standard Specification for Standard Masses and Balances Used in the Testing<br />
of Highway Materials<br />
MP1 Proposed Standard Specification for Performance-Graded Asphalt Binder<br />
zThis standardis basedon <strong>SHRP</strong>Product1003.<br />
61
T179 Test Method for Effect of Heat and Air on Asphalt Materials (Thin-Film Oven<br />
Test)<br />
T240 Test Method for the Effect of Heat and Air on a Moving Film of Asphalt<br />
(Rolling Thin Film Oven Test)<br />
2.2 ASTM Standards:<br />
E220 Method for Calibration of Thermocouples by Comparison Techniques<br />
2.3 DIN Standards:<br />
43760<br />
3. TERMINOLOGY<br />
3.1 Definitions<br />
3.1.1 asphalt binder, n--an asphalt-based cement that is produced from petroleum<br />
residue either with or without the addition of non-particulate organic modifiers.<br />
3.1.2 in-service, adj--refers to aging of the asphalt binder that occurs in the pavement<br />
as a result of the combined effects of time, traffic and the environment.<br />
4. SUMMARY OF TEST METHOD<br />
4.1 Asphalt binder is first aged using T240 (RTFOT) or T179 (TFOT). A specified<br />
thickness of residue, from the RTFOT or TFOT, is then placed (or left) in standard TFOT<br />
(T179) stainless steel pans and aged at the specified aging temperature for 20 hours in a<br />
vessel pressurized with air to 2.10 MPa. Aging temperature is selected according to the<br />
grade of the asphalt binder.<br />
5. SIGNIFICANCE AND USE<br />
5.1 This method is designed to simulate the oxidative aging that occurs in asphalt<br />
binders during pavement service. Residue from this test may be used to estimate the physical<br />
or chemical properties of an asphalt binder after five to ten years of aging in the field.<br />
5.2 Asphalt binders aged using PP1 are used to determine specification properties in<br />
accordance with MP1. The asphalt binder is aged with the RTFOT or TFOT prior to this<br />
conditioning step. Tank asphalt binders, as well as RTFOT or TFOT, and residue from this<br />
test are used to determine specification properties in accordance with MP1.<br />
62
5.3 For asphalt binders of different grades or from different sources, there is no<br />
unique correlation between the aging time and temperature in this test and in-service<br />
pavement age and temperature. Therefore, for a given set of in-service climatic conditions, it<br />
is not possible to select a single PAV aging time and temperature that will predict the<br />
properties of all asphalt binders after a specific set of in-service exposure conditions.<br />
5.4 The relative degree of hardening of different asphalt binders varies at different<br />
temperatures in the PAV. Therefore, two asphalt binders may age similarly at one<br />
temperature, but age differently at another temperature.<br />
6. APPARATUS<br />
6.1 The test system consists of a pressurized aging vessel (PAV), pressure<br />
controlling devices, temperature controlling devices, pressure and temperature measuring<br />
devices, and a temperature recording device (figure 1).<br />
6.1.1 Pressure Vessel--A stainless steel pressure vessel designed to operate at<br />
2.1 + 0.1 MPa between 90 and 110°C with interior dimensions no greater than 200 mm in<br />
diameter and 215 mm in height (adequate to hold 10 TFOT pans and pan holder). The<br />
pressure vessel shall contain a pan holder capable of holding 10 TFOT stainless steel pans in<br />
a horizontal (level) position such that the asphalt binder film thickness in the bottom of the<br />
pans does not vary by more than 0.1 mm across any diameter of the pan. The holder shall be<br />
designed for easy insertion and removal from the vessel when the holder, pans, and asphalt<br />
binder are at the test temperature. A schematic that shows the vessel, pan holder and pans,<br />
and the specific dimensional requirements is shown in figure 2.<br />
NOTE2.--The vessel may be a separate unit to be placed in a forced draft oven for conditioning the asphalt<br />
binders or an integral part of the temperature control system (for example, by direct heating of the vessel or by<br />
surrounding the vessel with a permanently affixed heating unit, forced air oven, or liquid bath).<br />
6.1.2 Pressure Controlling Devices<br />
6.1.2.1 A pressure release valve that prevents pressure in the vessel from exceeding<br />
2.2 MPa during the aging procedure<br />
6.1.2.2 A pressure regulator capable of controlling the pressure within the vessel to<br />
:t: 1 percent of the desired pressure, and with a capacity adequate to reduce the pressure<br />
from the source of compressed air so that the pressure within the loaded PAV is maintained<br />
at 2.1:1:0.1 MPa during the test<br />
6.1.2.3 A slow-release bleed valve that allows the pressure in the vessel at the<br />
completion of the conditioning procedure to be reduced at an approximately linear rate from<br />
2.1 MPa to local atmospheric pressure within 9 + 1 minutes<br />
6.1.3 Temperature Controlling Devices--A temperature control device as described in<br />
section 6.1.3.1 or 6.1.3.2 for maintaining the temperature during the aging procedure at all<br />
63
points within the pressure vessel at the aging temperature + 0.5°C and a digital proportional<br />
controller for maintaining the specified temperature control.<br />
6.1.3.1 A forced-draft oven or fluid bath capable of (1) bringing the loaded<br />
unpressurized vessel to the desired conditioning temperature + 0.5°C, as recorded by the<br />
resistance thermal detector (RTD) inside the vessel, within 2 hours, and (2) maintaining the<br />
temperature at all points within the pressure vessel at the aging temperature + 0.5°C. The<br />
oven shall have sufficiently large interior dimensions to allow forced air to freely circulate<br />
within the oven and around the pressure vessel when the vessel is placed in the oven. The<br />
oven shall contain a stand or shelf which supports the loaded pressure vessel in a level<br />
position above the lower surface of the oven (i.e., maintains the film thickness in the aging<br />
pans within the specified tolerance).<br />
6.1.3.2 A PAV with integral temperature control system that is capable of<br />
(1) bringing the loaded vessel to the desired conditioning temperature ___0.5°C within<br />
2 hours, as recorded by the RTD inside the PAV, and (2) maintaining the temperature at all<br />
points within the pressure vessel at the aging temperature + 0.5°C.<br />
6.1.4 Temperature and Pressure Measuring Devices<br />
6.1.4.1 A platinum RTD accurate to the nearest 0.1 °C and meeting DIN Standard<br />
43760 (Class A), or equal, for measuring the temperature inside the PAV. The RTD shall be<br />
calibrated as an integral unit with its respective meter or electronic circuitry.<br />
NOTE 3.--The RTD or thermistor and its meter may be calibrated by the manufacturer or a commercial<br />
vendor. Verification can be obtained by comparing the output from the RTD with a NIST-traceable ASTM 94C<br />
mercury-in-glass thermometer in accordance with ASTM E220. A stirred fluid bath is suitable for calibrating the<br />
thermal detector. Select a partial immersion mercury-in-glass thermometer with an appropriate range and place the<br />
thermal detector and the thermometer in the stirred water bath. Fasten the detector to the glass thermometer with a<br />
rubber band or rubber O-ring. Allow the bath, detector, and thermometer to come to thermal equilibrium and record<br />
the temperature of the glass thermometer and the readout from the thermal detector. The temperature in the bath<br />
shall not change by more than 0.1 °C per minute during the calibration process.<br />
6.1.4.2 Temperature Recording Device--A strip chart recorder or other data<br />
acquisition system capable of recording temperature throughout the test to 0.1 °C. As an<br />
alternative, an electronic device capable of reporting maximum and minimum temperatures<br />
(accurate to + 0.1 °C) may be used. In this case if the test temperature varies by more than<br />
+ 0.5°C of the conditioning temperature during the 20-hour period, the test shall be declared<br />
invalid.<br />
6.1.4.3 A pressure gauge capable of measuring the pressure in the PAV to + 1% of<br />
the desired pressure during the test.<br />
6.2 Stainless Steel Pans--Ten standard stainless steel TFOT pans meeting the<br />
requirements of T179.<br />
6.3 Balance--A balance conforming to the requirements of M231, Class G2.<br />
64
7. MATERIALS--Commercial bottled air or equivalent.<br />
8. HAZARDS--Use standard laboratory safety procedures in handling the hot asphalt binder<br />
when preparing test specimens and removing the residue from the PAV. Use special<br />
precaution when lifting the vessel.<br />
9. CALIBRATION AND STANDARDIZATION<br />
9.1 Temperature Detector--Verify the calibration of the RTD to 0. I°C at least every<br />
6 months using a calibrated thermometer.<br />
9.2 Pressure gauge--Calibrate the pressure gauge to an accuracy of 1% of the<br />
desired pressure at least every 6 months.<br />
NOTE4.--The pressure gauge is usually calibrated by the manufacturer or a commercial calibration service.<br />
Verification of the continued stability of the pressure gauge within the specified requirements should be done<br />
periodically by checking against another certified pressure measurement device.<br />
10. PROCEDURE<br />
10.1 Condition the asphalt binder and determine the mass change during conditioning<br />
in accordance with T240 (RTFOT) or T179 (TFOT).<br />
10.2 Combine the hot residue from the RTFOT into a single container, stir to blend,<br />
then transfer into (or leave in) TFOT pans for PAV conditioning or allow the hot residue in<br />
the container to cool to room temperature and cover and store at room temperature for PAV<br />
conditioning at a later date. If conditioned asphalt binder is allowed to cool to room<br />
temperature, heat it until it is sufficiently fluid to pour and stir it before pouring it into the<br />
TFOT pans. To remove asphalt binder from RTFOT bottles, scraping of the bottles is<br />
allowed, to assure sufficient material is obtained for later testing. Scraping is not currently<br />
allowed in T240. If scraping is used, report with the test results.<br />
10.3 Place the pan holder inside the PAV. If an oven is used, place the pressure<br />
vessel inside the oven. If an integrated temperature control pressurized aging vessel is used,<br />
turn on the heater. Select an aging temperature and preheat the vessel to the aging<br />
temperature selected.<br />
NOTE5.--If<br />
from table 1 of MP1.<br />
conditioning asphalt binders for conformance to MP1, select the appropriate aging temperature<br />
NOTE6.--Preheating the vessel 10 to 15"C above the conditioning temperature can be used to reduce the<br />
drop in PAV temperature during the loading process and minimize the time required to stabilize the system, after<br />
loading, to attain the required temperature.<br />
65
NOTE7.--Aging temperature in the PAV is selected to account for different climatic regions. Temperatures<br />
in excess of approximately 115°C can change the chemistry of asphalt binders aged in accelerated tests and should be<br />
avoided.<br />
10.4 Place the TFOT pan on a balance and add 50 + 0.5 gram mass of asphalt<br />
binder to the pan. This will yield approximately a 3.2-mm-thick film of asphalt binder.<br />
NOTE 8.--The mass change is not measured as part of this procedure. Mass change is not meaningful<br />
because the asphalt binder absorbs air as a result of pressurization. Any gain in mass as a result of oxidation is<br />
masked by air absorbed by the asphalt binder as a result of the pressurization.<br />
10.5 If the vessel is preheated to other than the desired aging temperature, reset the<br />
temperature control on the heating device to the aging temperature.<br />
10.6 Place the filled pans in the pan holder. Pans containing asphalt binders from<br />
different sources and grades may be placed in the pressure vessel during a single test. Place<br />
the panholder with filled pans inside the vessel and close the vessel.<br />
10.7 If an oven is used, place the loaded and closed vessel in the oven.<br />
10.8 Connect the temperature transducer line and the air pressure supply line to the<br />
loaded vessel's external connections.<br />
10.9 Perform the operations described in sections 10.5 to 10.8 as quickly as possible<br />
to avoid cooling of the vessel and pan holder.<br />
10.10 Wait until the temperature inside the pressure vessel is within 2"C of the aging<br />
temperature. Apply an air pressure of 2.1 + 0.1 MPa and then start timing the test. If the<br />
temperature inside the pressure vessel is not attained within two hours of loading, discontinue<br />
the test.<br />
NOTE 9.--Pressures in excess of 2.1 MPa do not substantially increase the rate of aging. Therefore, higher<br />
pressures are not warranted.<br />
NOTE 10.--Once pressurized, the temperature inside the pressure vessel will equilibrate rapidly. The time<br />
under pressure, not to include any preheating time at ambient pressure, is the aging time. Relatively little aging<br />
occurs at ambient pressure during the time that the vessel is being reheated to the test temperature, given that asphalt<br />
binder residue under test has been exposed to 163"C in the RTFOT.<br />
10.11 Maintain the temperature and air pressure inside the pressure vessel for<br />
20 hours + 10 minutes.<br />
10.12 At the end of the 20-hour test period, slowly begin reducing the internal<br />
pressure of the PAV, using the air pressure bleed valve. Adjust the bleed valve to an opening<br />
that requires 9 + 1 minutes to equalize the internal and external pressures on the PAV, thus<br />
avoiding excessive bubbling and foaming of the asphalt binder. During this process it may be<br />
necessary to adjust the setting of the needle valve as the pressure drops in order to maintain<br />
an approximate linear rate of pressure decrease. Do not include the pressure release and<br />
equalization time as part of the 20-hour aging period.<br />
66
10.13 If the temperature indicated by the temperature recording device falls above or<br />
below the target aging temperature _+0.5°C for more than 10 minutes during the 20-hour<br />
aging period, declare the test invalid and discard the material.<br />
10.14 Remove the pan holder and pans from the PAV, and place in an oven set at<br />
1630C. Heat until sufficiently fluid to pour. Stir gently to assist in the removal of air bubbles<br />
NOTE11.--Minimumpouringtemperaturesthatproducea consistencyequivalento thatof SAE10W30<br />
motoroil (readilypoursbutnotoverlyfluid)at roomtemperatureare recommended.Heatingunagedasphaltbinders<br />
to temperaturesabove135°Cshouldbe avoided.Somemodifiedasphaltsor heavilyagedbinders,however,may<br />
requirepouringtemperaturesabove135"C.PAVresiduemaybe heatedin theTFOTpansto 163°C andstirredto<br />
removeair bubbles.In allcasesheatingtimeshouldbe minimized.Theseprecautionswillhelpavoidoxidative<br />
hardeningandvolatilelossthat willhardenthe sample.Duringtheheatingprocessthesampleshouldbe coveredand<br />
stirredoccasionallyto ensurehomogeneity.<br />
10.15 Remove pans from oven and pour the hot residue from the pans into a single<br />
container. If tests to determine the properties of the PAV residue are not performed<br />
immediately, cover the container and store it at room temperature for future testing.<br />
11. REPORT<br />
11.1 Report the following information:<br />
11.1.1 sample identification;<br />
11.1.2 aging test temperature, to the nearest 0.5°C;<br />
11.1.3 maximum and minimum aging temperature recorded, to the nearest O.1°C;<br />
11.1.4 total time during aging that temperature was outside the specified range, to<br />
the nearest minute;<br />
11.1.5 total aging time, in hours and minutes.<br />
11.1.6 Report the heating temperature and heating time if temperatures greater than<br />
163°C are required at any time during the handling of the material,<br />
12. PRECISION AND BIAS<br />
12.1 Precision--The research required to develop precision estimates for tests<br />
performed on PAV residue has not been conducted.<br />
12.2 Bias--The research required to establish the bias of tests performed on PAV<br />
residue has not been conducted.<br />
67
13. KEY WORDS<br />
Accelerated aging, elevated temperature, in-service aging, PAV, pressure aging, pressure<br />
aging vessel.<br />
68
Bleed Valve<br />
Pressure Release Valve<br />
Pressure _,_ Regulat°r Pressure _. Gauge _ _ _ _ Needle Valve<br />
Rupture Disk<br />
Quick Disconnect<br />
......... •_.t...................<br />
Compressed Air Cylinder<br />
Temperature<br />
Control<br />
Figure 1. Schematic of Typical PAV Test System<br />
69
to temperaturetransducerand<br />
te_llperaturere_____ _r.ut<br />
_" _ > 10mm frOmde_OP of<br />
wall clearance_ 10mm _bm assembly to include<br />
F _-1 '. i' I N _ 10 TFOT pans<br />
I I , I I.=T_-..-._ supported on shelf or<br />
1 '1 I' I m standards.<br />
provide at least 5 nun _ ! ] t , , ] _ Entire assembly shall<br />
clearanceto nearest _ _--_ I ,' ' I I _ be removeable as an<br />
surface _.l ! U integral unR"<br />
_.mbly support _ _-I I ,' ' J, I M<br />
po.,<br />
Note 1: Distance a controls the levelness of the pans. The assembly shall be supported at three<br />
or more support points. The distance a, measured from each assembly support point<br />
to the bottom of the pan (top of shelf or pan support point), shall be controlled to<br />
+ 0.05 nun. Provision shall be made to ensure that the bottom of the vessel is leveled<br />
so that the thickness of the binder in the pans varies by no more than + 0.05 mm<br />
across the diameter of any pan.<br />
Note 2: Distance b shall be such that any active portion of the temperature transducer is<br />
>__10 mm from the top surface of the vessel.<br />
Note 3: Distance c shall be > 12 ram.<br />
Figure 2. Location of Pans and Resistance Thermal Detector within Representative PAV<br />
70
Standard Practice for<br />
Extraction and Recovery of Asphalt Cement<br />
for Rheological Testing<br />
<strong>SHRP</strong> Designation: B-0061<br />
1. SCOPE<br />
1.1 This test method describes the extraction and recovery of asphalt from<br />
bituminous concrete samples. It is to be used to determine the physical or chemical properties<br />
of an asphalt binder. It is not recommended for use in determining aggregate gradations.<br />
1.2 This procedure may involve hazardous materials, operations and equipment. This<br />
procedure does not purport to address all of the safety problems associated with its use. It is<br />
the responsibility of the user of this procedure to establish appropriate safety and health<br />
practices and determine the applicability of regulatory limitations prior to use.<br />
1.3 The values stated in SI units are to be regarded as the standard.<br />
2. APPLICABLE DOCUMENTS<br />
2.1 AASHTO Documents:<br />
T44<br />
Solubility of Bituminous Materials in Organic Solvents<br />
2.2 ASTM Standards:<br />
D979 Standard Practice for Sampling Bituminous Paving Mixtures<br />
D1856 Recovery of Asphalt from Solution by Abson Method<br />
D2172 Test Methods for Quantitative Extraction of Bitumen from Bituminous<br />
Mixtures<br />
Paving<br />
2.3 Other Documents:<br />
TRB papers 890445, 910350, 910352<br />
IThis standard is based on <strong>SHRP</strong> Product 1004.<br />
71
3. SUMMARY OF METHOD<br />
3.1 The paving mixture is repeatedly washed and filtered with solvents in the<br />
extraction/filtration apparatus shown in figure 1. Each filtrate is distilled under vacuum in a<br />
rotary evaporator with the asphalt remaining in the flask. After recovery of the final filtrate,<br />
the solution is concentrated and centrifuged to remove aggregate fines. The decanted solution<br />
is distilled under vacuum to remove the extraction solvents. Nitrogen gas is introduced<br />
during the final phase of distillation to drive off any remaining traces of solvents. The<br />
recovered asphalt (distillation residue) may then be subjected to further testing as required.<br />
4. SIGNIFICANCE AND USE<br />
4.1 The method can be used both for obtaining asphalt for further analyses and for<br />
calculation of asphalt content in pavement samples. Warning: The aggregate should not be<br />
used for sieve analysis because it undergoes prolonged grinding in the extraction device.<br />
5. APPARATUS AND MATERIALS<br />
5.1 Oven, capable of maintaining the temperature at 110°C __ 5°C<br />
5.2 Utilities--Vacuum source, nitrogen gas source, and cooling water source<br />
5.3 Balance, having an accuracy of at least .01% of the sample mass<br />
5.4 Extraction vessel (figures 2, 3, 4), a piece of aluminum pipe with removable<br />
upstream and downstream plates. The upstream plate (figure 5) has a mixing motor mount<br />
and a ¾ in addition port. The downstream plate (figure 6) is equipped with a ¼" in NDT<br />
quick connect fitting. Four 4 x 1 in baffles (figure 7) are mounted in the extraction vessel,<br />
followed by a 10-mesh screen, a glass wool plug, an 8-micron filter, and a 10-mesh backup<br />
screen.<br />
5.5 A fine filter (figure 8), consisting of a top (figure 9) and bottom (figure 10),<br />
each fabricated from 1/2in aluminum plate, which hold a 1-micron woven polypropylene<br />
filter and a 10-mesh stainless steel backup screen.<br />
5.6 Flask, suction, 500 mL<br />
5.7 Round bottom flasks, 1000 mL and cork stands<br />
5.8 Gas flowmeter, capable of indicating a gas flow up to 1000 mL/min<br />
5.9 Buchi Rotavapor RE-111A (or equivalent) with transfer and purge tubes<br />
5.9.1 Transfer tube, ¼ in polypropylene tubing 17 in long<br />
72
5.9.2 Purge tube, ¼ in polypropylene tubing 23 in long<br />
5.10 Hot oil bath, capable of heating oil to 177°C<br />
5.11 Copper tubing (note 1), amount adequate to connect apparatus as shown in<br />
figure 1<br />
NOTE 1.--The<br />
apparatus.<br />
quantity of copper tubing needed will be dependent upon the space utilized in setting up the<br />
5.12 Single Speed Mixing Motor, 150 W, 30 rpm<br />
5.13 Polypropylene Tubing (note 2), ¼ in for transferring solution throughout the<br />
procedure<br />
NOTE2.--To avoid contamination of the sample due to solvent degradation of the tubing, do not substitute<br />
Nalgene or rubber tubing for the polypropylene tubing specified.<br />
5.14 Woven polypropylene filter cloths--Coarse filter made from 2 x 2 twill weave,<br />
monofilament, 8 micron or 5 CFM rating, and fine filter made from oxford weave<br />
multifilament, 1-2 micron or .5 CFM rating<br />
5.15 Centrifuge, batch unit capable of exerting a minimum centrifugal force of 770<br />
times gravity<br />
5.16 Wide-mouth centrifuge bottles, 250 mL<br />
5.17 Thermometer, having a range of-2 to 300°C<br />
5.18 Glass wool, borosilicate<br />
5.19 Six 3-mm glass boiling beads<br />
6. REAGENTS<br />
6.1 Toluene, reagent grade<br />
6.2 Ethanol, absolute<br />
6.3 Nitrogen gas, at least 99.95% pure, in a pressurized tank, with pressurereducing<br />
valve.<br />
6.4 Argon gas, at least 99.99% pure, in a pressurized tank.<br />
73
7. PRECAUTIONS<br />
7.1 Solvents should be used only under a hood or with an effective surface exhaust<br />
system in a well-ventilated area.<br />
8. SAMPLING AND SAMPLE PREPARATION<br />
8.1 Obtain samples in accordance with ASTM D 979.<br />
8.2 If the mixture is not sufficiently soft to separate with a spatula or trowel, place it<br />
in a large, flat pan and warm to 110 + 5°C only until it can be handled or mixed. Split or<br />
quarter the material until 1000 g or the mass of material (note 3) required for the test is<br />
obtained.<br />
NOTE3.--This procedure works best for quantities of asphalt less than 60 g. Therefore, if the asphalt<br />
content of the mix is known, then the mass of sample required is that which yields about 50 to 60 g of asphalt.<br />
9. PROCEDURE<br />
9.1 Equipment Setup<br />
9.1.1 Prepare the extraction vessel by first installing the baffle pieces. Place the<br />
metal screen downstream of the baffle. Cut several pieces of glass wool and pack them in the<br />
space between the screen and the downstream end of the extraction vessel. Place gaskets,<br />
filter and aluminum end piece on extraction vessel, as shown in figure 3. Tightly and evenly<br />
fasten the end piece with wing nuts.<br />
9.1.2 Weigh an amount of pavement sample that will yield approximately 50 to 60 g<br />
of extracted asphalt. Place sample in extraction vessel. Put gasket and upstream end piece on<br />
the vessel and tightly and evenly fasten the wing nuts, creating a secure seal.<br />
9.1.3 Prepare the rotary evaporator. Turn on the cooling water. Turn on the oil bath<br />
and set the temperature to 100 +__2.5°C. Place six 3-mm glass boiling beads in a 1000-mL<br />
round bottom flask. Attach the recovery flask to the rotary evaporator and immerse 11/2in of<br />
the flask into the oil bath. Set the recovery flask at a 15° angle from the horizontal to the<br />
bath. Set the flask rotation at 40 rpm. Clamp the empty condensate flask onto the condenser.<br />
Attach transfer tube inside neck of rotary evaporator. Apply vacuum of 700 + 5-mm Hg to<br />
the rotary evaporator. Attach the filtrate transfer line to the external fitting on the neck of the<br />
rotary evaporator.<br />
9.2 Extraction and Filtration<br />
9.2.1 Charge 600 mL of toluene through the ¾-in port on the upstream end of the<br />
extractor. To purge the interior of the extraction vessel, inject nitrogen through the upstream<br />
74
port at 1000 mL/min for 1 minute. Close the port with a threaded plug. Attach the extractor<br />
to the motor. Start the motor and mix for 5 + 1 minutes at 30 rpm. Shut off the motor.<br />
9.2.2 Remove the extractor, place it on a stand and attach the quick connect fitting<br />
to the filtrate receiving flask. Make sure the filtrate transfer line is closed. Remove the<br />
upstream port and blanket the extractor with 400 mL/min of nitrogen while filtering. Apply<br />
700 + 5 mm Hg vacuum to the filtrate receiving flask. Filter until the filtrate flow rate is<br />
below 10 mL/min. Shut off the vacuum.<br />
9.2.2.1 If using the fine filter, switch vacuum to a second filtrate receiving flask and<br />
apply 700 + 5 mm Hg vacuum. Filter until filtrate flow rate is below 10 mL/min. Shut off<br />
vacuum.<br />
9.2.3 Disconnect the extractor from the quick connect fitting. Repeat the extraction<br />
procedure. For the second and third washes, use 400 + 10 mL of toluene. For subsequent<br />
washes (note 4), use 400 + 10 mL of toluene with 15 volume % ethanol. In addition, mix<br />
the second wash for ten minutes and all subsequent washes for 30 minutes or more.<br />
NOTE4.--It is suggested that after the third wash, the condensate from the primary distillation step be used<br />
for extraction solvent. Recycling solvent in this manner allows the entire procedure to use approximately 1500 mL<br />
toluene.<br />
9.3 Primary Distillation<br />
9.3.1 After filtration, open the filtrate transfer valve and allow the solution to flow<br />
from the filtrate receiving flask to the recovery flask. Continue the transfer until the filtrate<br />
receiving flask is empty or the recovery flask is about U8full.<br />
9.3.2 Close the filtrate transfer valve line and distill solvent at 100 + 2.5°C (oil<br />
bath temperature) and 700 + 5 mm Hg vacuum.<br />
9.3.3 If the condensate flask is over half full after the primary distillation step,<br />
empty the flask. Save this solvent for use in subsequent washes (note 4). After primary<br />
distillation of each filtrate, maintain vacuum, temperature, flask rotation, and cooling water.<br />
Repeat the primary distillation after each filtration (note 5).<br />
NoTE 5.--It is important to concentrate the asphalt in the recovery flask after each wash at a low<br />
temperature. This minimizes the time and temperature spent in dilute solution and therefore minimizes asphalt<br />
hardening in solvent.<br />
9.3.4 After primary distillation of the first three filtrates, remove the recovery flask<br />
(which should contain only small amounts of solvent) and set it aside. Replace it with another<br />
1000 mL roundbottom flask containing six 3-mm glass boiling beads.<br />
9.3.5 Carry out the remaining primary distillations using the new recovery flask.<br />
75
9.4 Final Extraction and Recovery<br />
9.4.1 If the filtrate flowing through the transfer tube is a light brown color after a<br />
30-minute wash, proceed to the final recovery step.<br />
9.4.2 Pour contents of the current recovery flask into the original recovery flask.<br />
Attach the original recovery<br />
flask to the Rotavapor.<br />
9.4.3 Distill the contents of the recovery flask until it is about 1/afull.<br />
9.4.4 Disconnect the recovery flask and pour the contents into the centrifuge bottles.<br />
Fill the bottles so that their weights are equal. Wash any residue from the recovery flask into<br />
the centrifuge bottles. Raise the oil bath temperature to 177 + 2.5°C. Centrifuge the bottles<br />
at 3600 rpm for 25 minutes.<br />
9.4.5 Decant the asphalt-solvent solution into the recovery flask and add six 3-mm<br />
glass boiling beads. Attach the flask to the rotary evaporator. Disconnect the transfer tube<br />
from the rotary evaporator and replace it with the gas purge tube. Disconnect the filtrate<br />
transfer line from the external rotary evaporator neck fitting and replace it with the nitrogen<br />
gas line. Apply 700 mm Hg vacuum. Lower the flask 11/2in into the oil bath.<br />
9.4.6 Distill the solvent.<br />
9.4.7 When the condensation rate falls below 1 drop every 30 seconds, introduce<br />
nitrogen gas at 1000 mL/min. Maintain the gas flow, vacuum and bath temperature for<br />
30 + 1 minutes to reduce the residual solvent concentration to near zero. Complete removal<br />
of residual solvent is very important for obtaining accurate asphalt properties.<br />
9.4.8 Shut down the oil bath, flask rotation, vacuum, gas flow, and cooling water.<br />
Remove the evaporating flask and pour the asphalt into a sample tin.<br />
NOTE 6.--A high temperature annealing step is recommended as a finishing step. This enables the asphalt<br />
molecules to "realign" themselves and promotes the attainment of an equilibrium state. Flood the asphalt container<br />
with argon and cover. Heat container to 163°C and maintain temperature for 2 hours. Place container in a paint<br />
shaker for 5 minutes, and then allow to cool to room temperature.<br />
10. PRECISION AND BIAS<br />
10.1 Repeatability and reproducibility tests have not been established in accordance<br />
with standard AASHTO practice.<br />
76
Extractor and Coarse Filter<br />
Fine Filter<br />
...... To Vac<br />
trt<br />
Is<br />
Centrifuge<br />
O°<br />
Flow Meter<br />
Nitrogen__<br />
Condensate<br />
(__<br />
Flask<br />
Flask<br />
Rotary Evaporator<br />
Figure 1. Asphalt Extraction and Recovery Apparatus<br />
77
Glass Wool Plug<br />
Figure 2. Extraction and Filtration Vessel<br />
78
_ _ 1) ¾-in stainless steel NPT plug<br />
2) Motor mount % in I.D. 'A-in NPT<br />
fitting<br />
3) 12 1/a-inwing nuts<br />
4) 12 2-in long 1/a-in screws<br />
5) Extraction Vessel Top (IA-in thick<br />
aluminum plate)<br />
6) 3 Viton Gaskets '/a-in thick, %-in width<br />
with holes to fit over studs<br />
7) Extraction Vessel (5-in long, 6-in ¢,<br />
Schedule D aluminum pipe)<br />
8) Aluminum Baffle Housing<br />
[[] it<br />
I I<br />
II<br />
I I<br />
it<br />
[ II<br />
10) 9) 2Aluminum stainless steel ring screens '/a-in thick, 10 mesh 5.75-in<br />
O.D., %-in width<br />
U I U LI IU 11) Glass Wool<br />
I I _ 12) SW230 8 micron Polypropylene Twill<br />
" {_7) Weave Filter with holes to fit over<br />
[ I - -- studs<br />
I [ 13) Extraction Vessel Bottom ('A-in thick<br />
I<br />
aluminum plate)<br />
I [ 14) Stainless Steel Quick Connect 1A-in<br />
n [ rl n [r I NPT fitting<br />
'11 I " II " II I" I! i<br />
[ Glass Wool Plug<br />
' ®<br />
®<br />
Figure 3. Exploded Diagram of Extraction and Filtration Vessel<br />
79
5.761 in I.D.<br />
6 holes 3/16 in I.D.<br />
3 1/8 in<br />
6.625 in<br />
I.I, l..l I,.I I I..I<br />
• "I .... I" "<br />
I<br />
I<br />
' ' 112 in<br />
I<br />
I<br />
I '"" " " "' l<br />
I<br />
I<br />
5 in i i<br />
I<br />
I<br />
I !<br />
I<br />
I<br />
I<br />
I<br />
I<br />
I<br />
I<br />
I<br />
I i 1/_'<br />
in<br />
! !<br />
I'! ! r-! r'l i r'l<br />
, ii I ii ii<br />
=<br />
I,I<br />
" ! °l<br />
I<br />
I<br />
6-in nominal schedule 80 aluminum pipe<br />
l<br />
Figure 4. Dimensions for the Extraction Vessel<br />
8O
112 I.D<br />
3/4 I.D. 6 holes 5/16 in I.D.<br />
1 112 in<br />
3 1/8 in<br />
-_ 6.625 in .<br />
! t t i i<br />
ill I I I IIi Ill _1!<br />
I" I ' I ' ' I' " I " I i_f_ 1/2in<br />
l_3 1/8<br />
in = 1/2 in<br />
Figure 5. Extraction Vessel Top<br />
81
1/4 I.D.<br />
5 3/4 in I.D.<br />
6 holes 5/16 in I.D.<br />
3 1/8 in<br />
I . 6.625 in -<br />
I i I I I<br />
=-_--I',,','-----;r,---.-l.<br />
....T_---",,', 1___.<br />
1/8 in I I I I I 1/2 in<br />
L 3 1"_/8in<br />
----_ 1 9/16 in<br />
Figure 6. Extraction Vessel Bottom<br />
82
5in<br />
I.D.<br />
Weld<br />
-= 5 3/4 in<br />
_/_<br />
|<br />
| ii<br />
1/8 in<br />
4 in<br />
I<br />
I<br />
---_ _-- 1in 1in ----_ "4"--<br />
4 aluminum plates 1/8 in thick<br />
2 Aluminum rings 5 3/4 in O.D., 5 in I.D.<br />
Figure 7. Baffle Housing<br />
83
Polypropylene Cloth<br />
Filter<br />
I" .......... "11<br />
Aluminum Circle<br />
13-in Diameter<br />
1/2 in Thick<br />
Steel Screen<br />
Figure<br />
8. Fine Filter (1 to 2 microns)<br />
84
1/4 in I.D. 1 1 1/4 in I.D.<br />
8 holes 5/16 in I.D.<br />
6 in<br />
-- 12 3/4 in =<br />
-F-I ,_,--+_I ' ' '_;-_"<br />
1/4in ,,, I _ I _ I ,,, I I_T 1/2in<br />
4--" 6in _1<br />
Figure 9. Top of the Fine Filter Housing<br />
85
114 in I.D.<br />
11 1/4 in I.D.<br />
8 holes 5/16 in I.D.<br />
6 in<br />
-_<br />
12 3/4 in<br />
i i | i<br />
i I i.. -- 4. |<br />
-T-l,,=, ,_,..... _-; _,-',=' I<br />
, ,--_<br />
1/8 in i I I 1/2 in<br />
6 in<br />
Figure 10. Bottom of the Fine Filter Housing<br />
86
Standard Method of Test for<br />
The Measurement of Initial Asphalt Adsorption<br />
and Desorption in the Presence of Moisture<br />
<strong>SHRP</strong> Designation: M-0011<br />
1. SCOPE<br />
1.1 This test method describes a procedure for assessing the ability of an asphalt<br />
cement to adhere to the surface of the fine aggregate portion of an asphalt concrete mixture.<br />
The strength of the initial adhesion of the asphalt cement to the aggregate in the presence of<br />
moisture can also be assessed.<br />
1.2 A sample of aggregate is exposed to a solution of asphalt cement in toluene at<br />
room temperature (25°C). After an equilibrium period, the amount of asphalt cement that has<br />
adsorbed on the aggregate is measured. Water is then introduced into the system, and it<br />
displaces the asphalt cement adsorbed on the aggregate surface. After a period of time, the<br />
amount of asphalt cement remaining on the aggregate is measured. This is the net adsorption<br />
amount.<br />
NOTE1.--This test methodmaynot be accuratefor modifiedasphaltbindersbecauseof potential<br />
differences in toluene solubilityand absorbancewavelengthbetween the base asphalt cementand the modifier. Use of<br />
the test method is recommended for unmodifiedasphalt binder-aggregatepairs only.<br />
1.3 The values stated in SI units are to be regarded as the standard.<br />
1.4 This standard may involve hazardous materials, operations, and equipment. This<br />
standard does not purport to address all of the safety problems associated with its use. It is<br />
the responsibility of the user of this standard to establish appropriate safety and health<br />
practices and determine the applicability of regulatory limitations prior to use.<br />
2. REFERENCED DOCUMENTS<br />
2.1 AASHTO Standard Method T40, Practicefor Sampling Bituminous Materials.<br />
2.2 Toluene--Consult manufacturer's or vendor's Material Safety Data Sheet (MSDS)<br />
for safety and handling precautions.<br />
1Thisstandard is based on <strong>SHRP</strong> Product 1013.<br />
87
3. SUMMARY OF TEST METHOD<br />
3.1 A solution of asphalt cement and toluene (approx 1.0 g/L) is prepared. Four<br />
milliliters of the solution is removed, diluted to a total volume of 25 mL in a volumetric<br />
flask, and the absorbance at 410 nm determined with a spectrophotometer which has been<br />
zeroed with pure toluene.<br />
3.2 Fifty grams of minus 4.75 mm aggregate is then added to a 500-mL Erlenmeyer<br />
flask, and 140 mL of the asphalt cement solution is added. The solution and aggregate are<br />
swirled on a shaker table for 6 hours.<br />
3.3 At this time a 4-mL sample of the solution is removed from the flask, diluted to<br />
25 ml, and the absorbance is again determined. The difference in the absorbance readings<br />
determines the amount of asphalt cement that has been adsorbed from the solution onto the<br />
aggregate surface due to the chemical attraction of the molecular components of the asphalt<br />
cement.<br />
3.4 Immediately after the second solution sample is taken, 2 mL of water is added to<br />
the flask. The solution is then shaken for another 8 or more hours. A final 4 mL of solution<br />
is taken from the flask at the end of this time, diluted, and the absorbance at 410 nm again<br />
determined. The increase in the absorptivity of the solution is a measure of the amount of<br />
asphalt cement that has been displaced by water molecules.<br />
4. APPARATUS<br />
4.1 Shaker Table--orbital shaker table equipped with holders to accept 500 mL<br />
Erlenmeyer flasks. The number of 500-mL flasks the shaker can accept will determine the<br />
number of samples that can be run in 24 hours. A typical small shaker table can accept nine<br />
flasks. The large shaker tables can accept more. A nine-position table will allow up to four<br />
asphalt-aggregate combinations to be run in a 24-hour period.<br />
NOTE2.--This test is designed to be conducted at room temperature (20 to 25°C). Laboratories should<br />
conduct this test in a temperature-controlled area. If the tests are to be conducted in an area with poor temperature<br />
control, an environmentally controlled shaker bath should be used to control the sample temperature at 25°C.<br />
4.2 Spectrophotometer--Capable of providing a continuous 410 nm wavelength with<br />
an accuracy of + 2 nm, and a precision of better than + 0.5 nm. The photometric precision<br />
should not be greater than + 0.2%. The unit shall be capable of receiving standard 10-mm<br />
path-length cuvettes and measuring absorbance between 0.000 and 1.999.1<br />
4.3 Spectrophotometer Cuvettes--Should have a capacity of at least 4.5 mL with a<br />
10-mm path length and suitable optical characteristics for measurements of wavelengths from<br />
375 to 410 nm (generally included with spectrophotometer).<br />
ISpectronic 20 (VWR 22348-106) has been found to be satisfactory.<br />
88
4.4 Erlenmeyer Flasks (500 mL)--wide-mouthed, with #10 neoprene stoppers.<br />
4.5 Erlenmeyer Flask (lO00 mL).<br />
4.6 Volumetric Flasks (25 mL)--Class A.<br />
4.7 Funnel--75 nun in diameter.<br />
4.8 Filter Paper--125 mm in diameter. 1<br />
4.9 Ring Stand and Clamps--stand and clamps should be sufficiently large to hold<br />
the funnels without danger of tipping over.<br />
4.10 Graduated Cylinder--glass, 250 mL capacity.<br />
4.11 Micropipettor--capable of being set to any volume from 1 to 10 mL and<br />
equipped with disposable tips.2<br />
4.12 Magnetic Stirrer and Stir Bar--small magnetic stirrer and appropriately sized<br />
stir bar capable of stirring asphalt binder in toluene solution.<br />
4.13 Analytical Balance--capacity of 500 g and sensitivity of + 0.001 g.<br />
4.14 Aggregate Drying Oven--capable of maintaining 135°C + 1.3°C.<br />
5. REAGENTS<br />
5.1 Toluene--UV or spectroanalyzed grade.<br />
5.2 Water--distilled or deionized water. Commercially available bottled water is<br />
acceptable.<br />
6. AGGREGATE PREPARATION<br />
6.1 Weigh a 50 + 0.3 g sample (weighed to the nearest 0.001 g) of the minus 4.75<br />
mm aggregate stockpile and dry, uncovered, in a 135°C oven for a minimum of 15 hours.<br />
6.2 Remove the sample from the oven at least 15 minutes prior to adding to the<br />
Erlenmeyer flask and store in a desiccator until needed. Samples not used within 24 hours of<br />
lWhatman No. 42 (VWR 28480-106) has been found to be satisfactory.<br />
2Eppendorf Maxipettor (VWR 53512-930) has been found to be satisfactory.<br />
89
drying should be re-dried. Caution: do not add warm aggregate to the toluene solution.<br />
Toluene has a low flash point.<br />
7. PREPARATION OF 1 g/L STOCK ASPHALT SOLUTION<br />
7.1 Place 500 mL of toluene in a 1,000 mL Erlenmeyer flask. Add approximately<br />
0.5 g of asphalt cement (weighed to the nearest 0.001 g) to the toluene. Record the weight of<br />
the asphalt cement on the data sheet (figure 1) and/or laboratory notebook, and calculate the<br />
initial concentration of the asphalt cement solution in g/L, recording to two decimal places.<br />
Add a magnetic stir bar to the flask. Place the flask on a magnetic stirrer. Agitate the<br />
solution for a minimum of 10 minutes or until the asphalt cement is dissolved.<br />
7.2 The appropriate amount of asphalt cement can be obtained by using a sharp knife<br />
to cut the sample out of a cooled can of asphalt cement.<br />
7.3 Only asphalt cement-toluene solutions prepared within 24 hours of starting the<br />
test should be used. Older solutions should be discarded.<br />
8. TEST PROCEDURE<br />
8.1 All glassware to be used in this procedure must be clean and dry. Use toluene to<br />
remove any asphalt cement remaining from previous tests. It is especially important to clean<br />
and dry spectrophotometer cuvettes after each use.<br />
8.2 Turn on the spectrophotometer and allow it to warm up in accordance with the<br />
manufacturer's recommendations. Once it has completed its internal calibration sequence, set<br />
the wavelength to 410 nm and zero the reference point with toluene according to the<br />
manufacturer's directions.<br />
8.3 For each asphalt-aggregate combination to be tested, label two 500 mL<br />
Erlenmeyer flasks (each sample is run in duplicate). For each aggregate to be tested, also<br />
label one Erlenmeyer flask as a "blank."<br />
8.4 Place 50 + 0.3 g of aggregate (weighed to the nearest 0.001 g) in each of the<br />
labeled flasks, including the blank flask. Record the aggregate weight on the data sheet<br />
and/or laboratory notebook.<br />
8.5 Using the 250-mL graduated cylinder, add 140 mL of plain toluene to the flask<br />
labeled "blank." Add 140 mL of freshly prepared asphalt cement solution to each of the<br />
other flasks, except the blank.<br />
8.5.1 The blank solution is carried through the entire procedure to insure that there is<br />
no material on the aggregate that will interfere with the test. It is expected that most<br />
materials will have very low absorbance values for the blank solutions. Some limestones,<br />
however, can contain considerable amounts of naturally occurring organic material which<br />
90
could interfere. If the absorbance values of the blank are greater than 0.010 for any of<br />
the readings, this absorbance value must be subtracted from all absorbance readings<br />
taken with that aggregate (A, and At).<br />
8.6 Stopper the flasks with a #10 neoprene stopper, and place each flask securely in<br />
the holder atop the shaker apparatus.<br />
8.7 Turn on the shaker and adjust the speed to approximately 300 rpm. The rate<br />
should be high enough to insure good mixing, but without danger of throwing the flasks off<br />
the table. Once the appropriate table speed is determined for the particular shaker, this same<br />
speed should be used for all tests run in the laboratory.<br />
8.8 Record the starting time on the data sheet and/or laboratory notebook.<br />
8.9 Using the micropipettor, transfer 4.00 mL of the stock asphalt cement solutions<br />
for each asphalt cement being tested into a clean, dry 25 mL volumetric flask, and dilute to<br />
the mark with fresh toluene. Holding the stopper on the flask with the fingers, invert the<br />
flask at least 6 times to mix the solution.<br />
8.10 Transfer about 4 mL of the diluted stock solution into a spectrophotometer<br />
cuvette, and determine the absorbance at 410 nm in the spectrometer. Record this value on<br />
the data sheet and/or laboratory notebook as "initial absorbance," or Ai.<br />
8.11 Using the ring stand and appropriate clamps, set up a funnel for each sample,<br />
with a clean, dry spectrophotometer cuvette under each funnel stem. Place a piece of folded<br />
filter paper in each funnel.<br />
8.12 After 6.0 hours, stop the shaker table, allow the solution to settle for<br />
10 minutes. Using the adjustable pipettor, transfer 4.00 mL of each solution to an<br />
appropriately marked clean, dry 25-mL volumetric flask. Dilute to the mark with clean<br />
toluene, stopper, and mix thoroughly by inverting the volumetric flask a minimum of six<br />
times while holding the stopper on with the fingers.<br />
8.13 Carefully pour sufficient contents of the 25-mL volumetric flasks into the funnel<br />
to filter at least 4 mL of solution into each of the cuvettes.<br />
8.14 Measure the absorbance of each cuvette at 410 nm in the spectrometer. Record<br />
this value on the data sheet and/or laboratory notebook under the heading "Abs. @ 6.0 hrs"<br />
or Aa.<br />
8.15 Using the adjustable micropipettor, transfer 2.00 mL of water to each of the<br />
500 mL Erlenmeyer flasks on the shaker table, replace the neoprene stoppers, and restart the<br />
shaker. Note the time on the data sheet and/or laboratory notebook. The shaker will now be<br />
allowed to run overnight while the water desorption step takes place.<br />
91
8.16 Clean the funnels, volumetric flasks, and cuvettes, dispose of the filter paper,<br />
and set up the funnels, as described in section 8.11. Make sure no residual asphalt cement is<br />
left on any apparatus. Residual toluene can be removed by gently blowing nitrogen or oilfree<br />
compressed air into the glassware inside a laboratory fume hood.<br />
8.17 In the morning, remove the flasks from the shaker table, and repeat steps 8.12,<br />
8.13, and 8.14, recording the absorbance value as the remaining absorbance (Ar) on the data<br />
sheet and/or laboratory notebook. Also record the time.<br />
8.18 Clean all glassware, dispose of used toluene in an appropriate waste container,<br />
and thoroughly dry all glassware before beginning another test sequence.<br />
9. CALCULATIONS<br />
9.1 Determine the amount of asphalt cement that was initially adsorbed onto the<br />
aggregate surface (report to two decimal places):<br />
where<br />
A_ (VC)(Ai-Aa)<br />
WAi<br />
A = Initial adsorption, mg/g.<br />
V = Volume in milliliters of solution in the flask at the time Aa is obtained,<br />
(normally 140 mL).<br />
W = Aggregate weight, in grams (section 8.4).<br />
C = Initial concentration of asphalt cement in solution, g/L. (section 7.1).<br />
Ai = Initial absorbance reading (section 8.10).<br />
A a = Absorbance reading after 6 hours (section 8.14).<br />
9.2 Determine the net adsorption (report to two decimal places):<br />
where<br />
An_<br />
(VC)(Ai-Ar)<br />
WAi<br />
An = Net adsorption, mg/g.<br />
V = Volume in milliliters of solution in the flask at the time Ar is obtained,<br />
(normally 136 mL).<br />
W = Aggregate weight, in grams (section 8.4).<br />
C = Initial concentration of asphalt cement in solution, g/L (section 7.1).<br />
Ai = Initial absorbance reading (section 8.10).<br />
Ar = Absorbance reading after water has been added to the column (section 8.17).<br />
test:<br />
9.3 Determine the percentage of asphalt cement remaining on the aggregate after the<br />
92
where<br />
%NA = Percent net adsorption.<br />
Ia ]×1®<br />
High values of %NA indicate increased resistance of the asphalt-aggregate<br />
stripping by water.<br />
bond to<br />
10. REPORT<br />
10.1 Figure 1 is a sample data sheet prepared to simplify entry of required<br />
measurements. It, or a similar form, shall be used to report the following:<br />
10.1 Ai--Initial absorbance readings at 410 nm.<br />
10.2 Aa--Absorbance readings at 410 nm after 6 hours.<br />
10.3 Ar--Absorbance readings at 410 nm after water desorption step.<br />
10.4 A--Initial absorption, mg/g.<br />
10.5 An--Net adsorption, mg/g_<br />
10.6 %NA--Percent net adsorption.<br />
11. NOTES<br />
11.1 Some sedimentary aggregates contain 1 or 2% naturally occurring organic<br />
compounds that could potentially interfere with this method. The use of a blank sample<br />
(section 8.4.1) will allow correction of this problem if it should occur.<br />
11.2 Highly adsorptive aggregates may not stabilize after the 6-hour adsorption<br />
period. If such an aggregate is suspected, the adsorption period should be extended and<br />
additional adsorption measurements taken as described in sections 8.12, 8.13, and 8.14.<br />
These values can then be calculated using the equation in 9.1, after adjusting the volume V of<br />
the sample to reflect the additional amounts of toluene removed from the flask. The proper<br />
adsorption time can be determined when the adsorption values stabilize, and no more<br />
additional asphalt cement is being adsorbed by the aggregate. A similar caution is also<br />
appropriate for the desorption step.<br />
93
Adsorption/Desorption<br />
Testing Data Sheet<br />
Date:<br />
Aggregate:<br />
Asphalt Cement:<br />
Asphalt Sample Weight (g). Stock Solution Concentrate (g/L)<br />
Reading IITime Flask #1 Flask #2 Flask #3<br />
Sample Weight,<br />
g<br />
Initial Abs. (Ai)<br />
Abs. @ 6.0 hrs. (A_)<br />
Blank Abs. @ 6 hrs.<br />
Abs. after Overnight<br />
(Ar)<br />
Initial Absorption<br />
(A)<br />
Net Adsorption<br />
(An)<br />
% Net Adsorption<br />
Aggregate:<br />
Asphalt Cement:<br />
Asphalt Sample Weight (g) Stock Solution Concentrate (g/L)<br />
Reading [[ Time Flask #1<br />
Flask #2 Flask #3<br />
Sample Weight,<br />
g<br />
Initial Abs. (Ai)<br />
Abs. @ 6.0 hrs. (Aa)<br />
Blank Abs. @ 6 hrs.<br />
Abs. after Overnight<br />
(At)<br />
Initial Absorption<br />
(A)<br />
Net Adsorption<br />
(An)<br />
% Net Adsorption<br />
Figure 1. Sample Net Adsorption<br />
Test Data Sheet<br />
94
Standard Method of Test for<br />
Preparation of Compacted Specimens of<br />
Modified and Unmodified Hot Mix Asphalt<br />
by Means of the <strong>SHRP</strong> Gyratory Compactor<br />
<strong>SHRP</strong> Designation: M-0021<br />
1. SCOPE<br />
1.1 This method covers the compaction of 100- or 150-mm diameter test specimens<br />
of modified or unmodified hot mix asphalt (HMA) and the measurement of specimen density<br />
during the compaction procedure.<br />
1.2 This standard may involve hazardous materials, operations, and equipment. This<br />
standard does not purport to address all of the safety problems associated with its use. It is<br />
the responsibility of the user of this standard to establish appropriate safety and health<br />
practices and determine the applicability of regulatory limitations prior to use.<br />
1.3 The values stated in SI units are to be regarded as standard.<br />
2. REFERENCED DOCUMENTS<br />
2.1 AASHTO Standards:<br />
T67 Standard Practices for Load Verification of Testing Machines<br />
T166 Bulk Specific Gravity of Compacted Bituminous Mixtures<br />
T209 Maximum Specific Gravity of Bituminous Paving Mixtures<br />
T269 Percent Air Voids in Compacted Dense and Open Bituminous Paving Mixtures<br />
2.2 <strong>SHRP</strong> Test Methods:<br />
M-007 Short- and Long-Term Aging of Bituminous Mixtures<br />
P-004 Volumetric Analysis of Compacted Hot Mix Asphalt<br />
P-005 Measurement of the Permanent Deformation and Fatigue Cracking Characteristics of<br />
Modified and Unmodified Hot Mix Asphalt<br />
1Thisstandardis basedon <strong>SHRP</strong>Product 1014.<br />
95
2.3 ASTM Standards:<br />
D 4402 Measurement<br />
of Asphalt Viscosity Using a Rotational Viscometer<br />
3. SUMMARY OF TEST METHOD<br />
3.1 The gyratory compactor produces a cylindrical test specimen from a loose<br />
modified or unmodified paving mix through a combination of parallel end pressure and<br />
gyratory kneading.<br />
3.2 A loose paving mix is prepared in the laboratory; short-term oven aged in<br />
accordance with AASHTO M-007; brought to the proper compaction temperature; and placed<br />
into a mold. The mold is placed in the compaction device and an end pressure of 600 kPa is<br />
applied by means of a vertical ram.<br />
3.3 Alternatively, loose plant mix is obtained; immediately brought to the proper<br />
compaction temperature; and placed into a mold. The mold is placed in the compaction<br />
device and an end pressure of 600 kPa is applied by means of a vertical ram.<br />
3.4 The mold is set for a 1.25 ° angle of gyration and the specimen is gyrated at<br />
30 rpm to a predetermined number of gyrations, based on the anticipated traffic for the<br />
roadway.<br />
3.5 The height of the specimen is recorded after each revolution and is used to<br />
calculate the specimen volume. The weight of the mixture and the specimen volume are used<br />
to estimate the specimen density.<br />
3.6 When the compaction is completed, the mold is removed and the test specimen<br />
is extruded for density determination using test method AASHTO T166.<br />
3.6.1 The extruded specimen is not a right angle cylinder. If the specimen is to be<br />
used for accelerated performance-based tests, the ends must be sawed to conform to the<br />
requirements of <strong>SHRP</strong> P-005.<br />
4. SIGNIFICANCE AND USE<br />
4.1 The specimens are compacted to simulate the density, aggregate orientation,<br />
and structural characteristics obtained in the actual road surface when proper construction<br />
procedure is used in the placement of the paving mix. The specimens may be used to<br />
determine a number of characteristics of bituminous mixtures by specified test methods.<br />
5. APPARATUS<br />
96<br />
5.1 Oven--Range at least 40 to 150°C, thermostatically controlled to + 3°C
5.2 Gyratory Compactor--Hydraulic compactor with ram and ram heads (see<br />
section 5.4) that are restrained from revolving during compaction. The axis of the ram shall<br />
be perpendicular to the platen of the compactor. The ram must maintain a pressure of 0.60<br />
_+0.01 MPa over 100- and 150-mm diameter specimen cross sections.<br />
NOTE 1.--This<br />
stress calculates to 4,710 ± 80 N and 10,600 ± 180 N total force.<br />
The compactor must tilt and gyrate the mold at an angle of 21.8 + 0.3 mrad<br />
(1.25 + 0.02 °) throughout compaction. The mold must be free to revolve on its tilted axis<br />
during gyration. Captive inside the mold is a mold bottom (see section 5.4) that is not<br />
attached in any way and shall be free to rotate on the lubricated platen of the compactor.<br />
Means shall be provided to continuously measure and digitally display the height of the<br />
specimen in mm during compaction and to transmit the height via an RS232C serial<br />
connection to the computer (see section 5.5) once per gyration. The speed of gyration shall<br />
be 30.0 + 0.5 gyrations per minute.<br />
5.3 Molds--Each mold shall be a minimum of 8.5-mm-thick steel hardened to at<br />
least Rockwell C48. Inside finishes shall have a root mean square (rms) of 16 or smoother.<br />
The dimension of the molds shall be:<br />
5.3.1 an inside diameter of 99.95 to 100.00 mm and a minimum of 160 mm (6.3<br />
in.) high; 0.05 mm wear allowed;<br />
5.3.2 an inside diameter of 149.95 to 150.00 mm and a minimum of 225 mm high;<br />
0.05 mm wear allowed.<br />
5.4 Ram Heads and Mold Bottoms--All shall be steel hardened to at least Rockwell<br />
C48. The ram heads shall have means for staying fixed to the ram and being perpendicular to<br />
its axis. The platen side of each mold bottom shall be flat and parallel to its face. All faces<br />
(the sides presented to the specimen) shall be ground fiat and have one of the following<br />
diameters:<br />
5.4.1 99.70 to 99.75 mm; 0.05 mm wear allowed;<br />
5.4.2 149.70 to 149.75 mm; 0.05 mm wear allowed.<br />
port<br />
5.5 Computer--IBM-compatible, with hard drive, diskette drive and RS232C serial<br />
5.6 Software--Capable of establishing specimen header information; receiving and<br />
recording height of specimen data once per gyration; and subsequently adding and editing<br />
header information in each specimen record with the following fields:<br />
5.6.1 Project name;<br />
5.6.2 Date of test;<br />
97
5.6.3 Start time of test;<br />
5.6.4 Specimen identification;<br />
5.6.5 Percent binder in specimen;<br />
5.6.6 Average diameter of mold used, in ram;<br />
5.6.7 Mass of specimen, in g;<br />
5.6.8 Maximum specific gravity (Gram)of specimen;<br />
5.6.9 Bulk specific gravity (Grab) of specimen;<br />
5.6.10 Successive heights of specimen, in mm.<br />
NOTE2.--It is expectedthatthe densityof everyspecimenaftergyrationnumber10willapproacha<br />
straightlinewhenplottedversusthe base 10logarithmofthe numberof gyrations.Theline willbecomeasymptotic<br />
as it approaches100%of G_.<br />
5.7 Miscellaneous<br />
5.7.1 Items in referenced standards (see section 2.1)<br />
5.7.2 Pan, metal, with a flat bottom, for heating aggregates<br />
5.7.3 Pans, metal, round, approximately 4-L (4-qt) capacity, for mixing asphalt<br />
and aggregates<br />
5.7.4 Oven and Hot Plate, electric, for heating aggregates, asphalt, and equipment<br />
as required. Oven must also be capable of maintaining temperature for short-term aging.<br />
5.7.5 Scoop, for hatching aggregates<br />
asphalt<br />
5.7.6 Containers, gill-type tins, beakers, pouring pots, or sauce pans, for heating<br />
5.7.7 Thermometers, armored, glass, or dial-type with metal stem, 10 to 232°C,<br />
for determining temperature of aggregates, asphalt and asphalt mixtures.<br />
5.7.8 Balances, one of 5-kg capacity, sensitive to 1 g, for weighing aggregates and<br />
asphalt, and one of 2-kg capacity, sensitive to 0.1 g, for weighing compacted specimens.<br />
5.7.9 Mixing Spoon, large, or Trowel, small<br />
5.7.10 Spatula, large<br />
98
5.7.11 Mechanical Mixer, commercial bread dough mixer 4-L capacity or larger,<br />
equipped with two metal mixing bowls and two wire stirrers<br />
5.7.12 Gloves, welders', for handling hot equipment.<br />
6. MATERIALS<br />
6.1 Paper disks--lO0- and 150-mm in diameter.<br />
6.2 Oil--Light lubricant.<br />
7. HAZARDS<br />
7.1 Proper precautions and protective clothing must be used when handling the hot<br />
paving mix to prepare test specimens.<br />
8. PREPARATION OF APPARATUS<br />
8.1 Immediately before the paving mix is ready to be placed in the mold, turn on<br />
the main power to the gyratory compactor and the LVDT readout.<br />
necessary.<br />
NOTE3.--Check<br />
to be sure that the ram compaction head is the same size as the mold, and change if<br />
8.2 Without a specimen in the compaction apparatus, calibrate the vertical pressure<br />
to 600 :i: 10 kPa.<br />
8.3 Verify that the automatic counter is reset and is set to shut off when the proper<br />
number of gyrations has been reached. This is based on the maximum number of gyrations<br />
for a specific mix design.<br />
8.4 Verify that the LVDT readout is in the proper units (mm), and that the<br />
recording device is ready.<br />
8.5 Lightly oil the surface of the rotating base and the surfaces of the four rollers.<br />
8.6 Prepare the computer to record the height data and enter the header information<br />
for the specimen.<br />
9. TEST SPECIMENS<br />
9.1 Prepare the paving mix.<br />
99
9.1.1 Weigh the aggregate fractions for each test specimen in a separate pan.<br />
Sufficient aggregate should be used so that the compacted specimen is 50 + 1 mm high. This<br />
normally is 2.1 kg. A trial specimen can be prepared and compacted to determine whether<br />
the amount of aggregate should be increased or reduced. Prepare an additional pan for<br />
determination of the maximum theoretical specific gravity.<br />
9.1.2 Place the pans in the oven and heat to a temperature approximately 30°C<br />
above the required mixing temperature. Charge the mixing bowl with the heated aggregates<br />
and dry mix thoroughly.<br />
9.1.3 Form a crater in the dry, blended aggregate and add the required amount of<br />
asphalt binder into the mix. Verify that the temperature of the asphalt binder and aggregate<br />
is within a range at which the kinematic viscosity of the unaged asphalt binder is<br />
170 + 20 mm2/s (approximately 0.17 ___0.02 Pa.s for an asphalt binder density of<br />
1.000 g/cm 3) measured in accordance with ASTM D 4402.<br />
NOTE4.--The SI unit of kinematic viscosity is m2/s; for practical use, the submultiple mm2/s is<br />
recommended. The more familiar centistoke is a cgs unit of kinematic viscosity; it is equal to 1 mm2/s. The<br />
kinematic viscosity is the ratio of the viscosity of the asphalt binder to its density. For an asphalt binder with a<br />
density equal to 1.000 g/cm 3, a kinematic viscosity of 170 mm2/s is equivalent to a viscosity of 0.17 Pa.s measured<br />
with the rotational viscometer by ASTM D 4402.<br />
9.1.4 Mix the aggregate and asphalt binder with the mechanical mixer as quickly<br />
and thoroughly as possible to yield a paving mix that has a uniform distribution of asphalt<br />
binder.<br />
NoTE 5.--Do not hold the asphalt binder at mixing temperature for more than 1 hour before using.<br />
9.2 After completing the mixture preparation, place the loose mix in a shallow, flat<br />
pan and short-term age it in a forced-draft oven in accordance with <strong>SHRP</strong> M-007.<br />
9.3 Using a companion sample, determine the maximum specific gravity of the<br />
loose mix in accordance with AASHTO T209.<br />
9.4 Place the compaction mold in a 135°C oven for 45 to 60 minutes prior to the<br />
estimated beginning of the compaction (during which time the mixture is being conditioned in<br />
accordance with M-007).<br />
9.5 At the end of the 4-hour conditioning period of <strong>SHRP</strong> M-007, remove the pan<br />
of paving mix from the oven and allow it to achieve the proper compaction temperature.<br />
9.5.1 he compaction temperature range is defined as the range of temperatures<br />
where the unaged asphalt binder has a kinematic viscosity of 280 + 30 mm2/s (approximately<br />
0.28 -t- 0.03 Pa.s) measured in accordance with ASTM D 4402.<br />
NOTE 6.--If the compaction temperature is greater than 135°C, the mix is placed in another oven for a<br />
brief time (maximum of 30 minutes) to achieve the required temperature.<br />
100
9.6 Once the compaction temperature is achieved, remove the heated mold, with<br />
the base plate, from the oven. Place a paper disk on the bottom of the mold.<br />
9.6.1 The mixture is placed into the mold in three layers. One-third of the mix is<br />
placed into the mold and then spaded five times with the mix scoop. This process is repeated<br />
for the next third and the final third. After all of the mix is in the mold, the mix is leveled<br />
and another paper disk is placed on top.<br />
NOTE7.--The spading process is used primarily for specimens of a coarse mixture. This process helps<br />
minimize segregation of the specimen at the boundaries.<br />
10. COMPACTION PROCEDURE<br />
10.1 Load the specimen into the gyratory compactor.<br />
NOTE 8.--Ensure<br />
that the mold is centered under the loading ram.<br />
10.2 Lower the ram until the pressure on the specimen reaches 600 kPa + 10 kPa.<br />
10.2.1 Apply the 1.25 ° _ 0.02 ° tilt to the mold assembly.<br />
10.2.2 Begin the gyratory compaction. Record the specimen height after each<br />
revolution. Allow the compaction to proceed until the maximum number of gyrations is<br />
reached and the gyratory mechanism shuts off.<br />
10.2.3 Remove the angle from the mold assembly and raise the loading ram.<br />
10.3 Remove the mold from the compactor.<br />
10.3.1 Extrude the specimen from the mold.<br />
NOTE 9.--This can be accomplished immediately for most HMA paving mixes. For lean, rich, or tender<br />
mixtures, a cooling period of 5 to 10 minutes may be necessary before extruding the specimen.<br />
NOTE 10.--Specimens produced having a final density less than 93 % of maximum theoretical density<br />
should be cooled 5 to 10 minutes before extruding the specimens to prevent deformation.<br />
10.3.2 Remove the paper disks from the top and bottom of the specimen.<br />
NOTE 11.--Before reusing the mold, place it in an oven for at least 5 minutes. The use of multiple molds<br />
will speed up the compaction process.<br />
10.4 Cool the specimen and determine its mass and bulk specific gravity in<br />
accordance with AASHTO T166.<br />
101
11. CALCULATIONS AND INTERPRETATION OF RESULTS<br />
11.1 Report--Magnetic recording on diskette with one record per specimen as<br />
specified in section of 5.6.<br />
11.2 Transmittal--Written and signed acknowledgement of work performed and<br />
observations of any unusual conditions and unexpected results.<br />
12. PRECISION AND BIAS<br />
12.1 Precision--The precision of the procedure in test method M-O02 for<br />
measuring density is being determined.<br />
12.2 Bias--Bias, if any, in test method M-O02 for measuring density is being<br />
determined.<br />
13. KEY WORDS<br />
Compaction,<br />
density, gyratory.<br />
102
Standard Method of Test for<br />
Determining the Shear and Stiffness Behavior<br />
of Modified and Unmodified Hot Mix Asphalt<br />
with the SUPERPAVE ®Shear Test Device<br />
<strong>SHRP</strong> Designation: M-0031<br />
1. SCOPE<br />
1.1 This standard is used to determine the permanent deformation and fatigue<br />
cracking characteristics of a bituminous mix. A series of tests are conducted at several<br />
temperatures and frequencies in during which the specimen is subjected to repeated axial and<br />
shear loads.<br />
1.2 The values stated in SI units are to be regarded as the standard.<br />
1.3 This standard may involve hazardous materials, operations and equipment. This<br />
standard does not purport to address all of the safety problems associated with its use. It is<br />
the responsibility of the user of this standard to establish appropriate safety and health<br />
practices and determine the applicability of regulatory limitations prior to use.<br />
2. APPLICABLE DOCUMENTS<br />
2.1 AASHTO Standards:<br />
T269<br />
Percent Air Voids in Compacted Dense and Open Bituminous Paving Mixes<br />
2.2 Other documents:<br />
M002 Preparation of Test Specimens by Means of Gyratory Compaction<br />
M008 Preparation of Test Specimens by Means of Rolling Wheel Compaction<br />
The SUPERPAVE ® Mix Design Manual for New Construction and Overlays<br />
3. APPARATUS AND MATERIALS<br />
NB: The following instructions relate specifically to the <strong>SHRP</strong> Shear Test<br />
Device. These instructions may be inappropriate for other test equipment.<br />
_This standard is based on <strong>SHRP</strong> Product 1017.<br />
103
3.1 Test System--The test system is capable of applying both vertical and horizontal<br />
loads to a specimen. It is also capable of applying static, ramped (increasing or decreasing)<br />
and repetitive loads of various waveforms. Loading is provided by two hydraulic actuators<br />
(vertical and horizontal) and controlled by closed-loop feedback. Figure 1 illustrates a typical<br />
loading condition.<br />
The computer-controlled system is capable of recording load cycles, applied horizontal and<br />
vertical loads, and specimen deformation in all directions (axial, horizontal and radial).<br />
Provisions have also been made for environmental control and monitoring.<br />
As a minimum,<br />
the test system should meet the following requirements.<br />
Load Measurement and Control<br />
Range:<br />
Resolution:<br />
Accuracy:<br />
0 to 32 kN<br />
0.02 kN<br />
+ 0.04 kN<br />
Confining Pressure Measurement and Control<br />
Range:<br />
Resolution:<br />
Accuracy:<br />
0 to 700 kPa<br />
0.7 kPa<br />
+ 1.4 kPa<br />
Deformation Measurement and Control<br />
Horizontal (Repetitive Shear) Horizontal (Frequency Sweep)<br />
Vertical (Constant Height, Frequency Sweep)<br />
Range: 5 mm Range: + 0.05 mm<br />
Resolution: 0.0025 mm Resolution: 0.0013 mm<br />
Accuracy: + 0.005 mm Accuracy: + 0.0025 mm<br />
Radial<br />
Range:<br />
Resolution:<br />
Accuracy:<br />
+ 1.02 mm<br />
0.005 mm<br />
+ 0.01 mm<br />
104
Temperature Measurementand Control<br />
Range: -10°C to 80°C<br />
Resolution: 0.25 °C<br />
Accuracy: + 0.5 °C<br />
3.2 Platen-Specimen Assembly Device (figure 2)--This device is used to facilitate<br />
bonding of the specimen to loading platens. The device maintains the platens in a parallel<br />
position (relative to each other) when the specimen is glued to them. The platens must be<br />
parallel so that stresses do not develop in the specimen when the specimen-platen assembly is<br />
clamped in the test system.<br />
3.3 Miscellaneous Apparatus and Materials:<br />
3.3.1 calipers for measuring specimen height and diameter;<br />
3.3.2 aluminum loading platens;<br />
3.3.3 quick-set adhesive with a minimum hardened stiffness modulus of 2,070 MPa<br />
for bonding platens to specimen ends;<br />
3.3.4 rubber membrane for uniform application of confining pressure;<br />
3.3.5 silicone sealant to seal membrane against platens;<br />
3.3.6 O-rings to secure ends of rubber membrane on platens;<br />
3.3.7 6-mm diameter plastic tube to be inserted between membrane and specimen so<br />
as to relieve any internal air pressure;<br />
3.3.8 device(s) for mounting LVDTs.<br />
4. TEST SPECIMENS<br />
4.1 Compact Asphalt Concrete Specimens--Specimens should be compacted in<br />
accordance with procedures outlined in section 2.2. Specimen dimensions should be 150 mm<br />
in diameter and 50 to 65 mm in height for mixes containing a maximum aggregate size of<br />
19 mm or less. i<br />
4.2 Measure Specimen Size--Measure the height and diameter of the specimen at<br />
three different points around its perimeter and report to the nearest 0.025 mm. Average the<br />
three measurements and report to the nearest 0.25 mm.<br />
lit is recommended that specimen dimensions be 200 mm in diameter by 75 mm in height for mixes containing a<br />
maximum aggregate size greater than 38 mm.<br />
105
4.3 Determine Air Void Content--Determine the air void content in accordance with<br />
AASHTO T-269-80.<br />
4.4 Bonding Specimen to Platens (Required for all tests except volumetric)--Place<br />
platens in the platen-specimen assembly device. Spread thin layer of adhesive (= 1.5 mm)<br />
on the top and bottom of specimen and the matching face of platen. Lower the top platen<br />
onto the specimen and rotate the specimen one full revolution to ensure an even distribution<br />
of adhesive between specimen and platens. (Do not block pressure-relief port on the platen<br />
with adhesive during the gluing process.) Insert a plastic pressure-relief tube into the port<br />
provided in the bottom platen. Follow the adhesive manufacturer's instructions for the time<br />
and temperature required to achieve full strength in the adhesive. Leave the specimen in the<br />
assembly device until the adhesive has set.<br />
4.5 Application of Elastic Membrane (Required for volumetric and uniaxial tests)-<br />
Spread a very thin layer of silicone sealant around the perimeter of each platen where the<br />
elastic membrane will be in contact with the platen. Stretch the membrane over the top platen<br />
and slide it down over the specimen, the pressure-relief tube and the bottom platen. Place the<br />
rubber O-rings around the top and bottom of the membrane in the grooves provided around<br />
the perimeter of each platen (figure 3).<br />
4.6 Stabilize Specimen to Test Temperature--Place the specimen in an oven or other<br />
environmentally controlled unit for a minimum of two hours prior to testing to ensure that<br />
specimen is at the specified test temperature.<br />
5. TEST PROCEDURES<br />
5.1 Volumetric Test<br />
5.1.1 Specimen Setup--Attach 2 vertical and 1 radial LVDTs to the specimen as<br />
shown in figure 4. The vertical LVDTs are used to measure changes in specimen height as<br />
represented by changes in the distance between the top and bottom platens. The radial<br />
LVDT, which measures changes in the specimen perimeter, should be mounted around the<br />
specimen at mid-height and move freely. Completely lower the environmental chamber to<br />
seal off the specimen from the outside temperature influences. Testing is conducted at<br />
temperatures of 4°C, 20°C, and 40°C + 0.5°C.<br />
5.1.2 Testing--Precondition specimen by applying a confining pressure of 70 kPA<br />
for 1 second and then immediately reduce the confming pressure to about 7 kPa. After<br />
preconditioning, apply the confining pressure at a rate of 70 kPa per second until reaching<br />
the desired level: 550, 690, or 830 kPa at 40, 20, or 4°C, respectively (figure 5). The<br />
confining pressure is applied for a total of 10 seconds, after which the confining pressure is<br />
relieved at a rate of about 23 kPa per second until reaching a residual confining pressure of<br />
about 7 kPa. Continue recording deformation for an additional 30 seconds during this<br />
recovery period. Axial and radial deformation, as well as axial load and confining pressure,<br />
should be recorded at appropriate intervals during the test, i.e., approximately 10 data points<br />
per second.<br />
106
The following test parameters<br />
should be recorded.<br />
• (711= 0-22= 033; confining pressure<br />
• _v = vertical displacement of the specimen<br />
• _ih = radial displacement of the specimen<br />
The following engineering<br />
quantities should be calculated.<br />
• eH= e22= e33= 6Jh; uniaxial strain where h is the height of the specimen<br />
5.2 Uniaxial Test<br />
5.2.1 Specimen Setup--The test setup is essentially identical to that for the<br />
volumetric/hydrostatic test with one exception: a 75-mm circular loading unit is placed<br />
between the load cell and top cap to create a more nearly uniform stress distribution. Attach<br />
2 vertical and 1 radial LVDTs to the specimen as shown in figure 4. The vertical LVDTs are<br />
used to measure changes in specimen height as represented by changes in the distance<br />
between the top and bottom platens. The radial LVDT, which measures changes in the<br />
specimen perimeter, should be mounted around the specimen at mid-height and move freely.<br />
Completely lower the environmental chamber to seal off the specimen from the outside<br />
temperature influences. Testing is conducted at temperatures of 4°C, 20°C, and<br />
40°C + 0.5°C.<br />
Position the vertical test system head to allow the specimen-platen assembly to slide between<br />
the bottom horizontal and top vertical heads. Position the horizontal test head such that the<br />
top and bottom test heads are aligned vertically. Slide the specimen between the heads so that<br />
it is centered between the heads. Secure the platens to the heads by activating the hydraulic<br />
clamps.<br />
5.2.2 Testing--Precondition the specimen by applying an axial load corresponding to<br />
an axial stress of 70 kPa in 1 second, then immediately reduce the load such that the axial<br />
stress is about 7kPa. After preconditioning the specimen, apply an axial load to induce an<br />
axial stress at a rate of 70 kPa per second until reaching the desired level: 345,415 and<br />
655 kPa at 40, 20 and 4°C, respectively (figure 6). The axial load is applied for a total of<br />
10 seconds, after which the axial load is relieved to achieve the release of the axial stress at<br />
rate of about 23 kPa per second until reaching a residual stress of about 7 kPA. (The<br />
confining pressure is adjusted by closed loop feedback control from the radial LVDT<br />
measuring the change in perimeter.) Continue recording data for an additional 30 seconds<br />
during this recovery period. Axial and radial deformations, as well as axial load and<br />
confining pressure should be recorded at appropriate intervals during the test, i.e.,<br />
approximately 10 data points per second.<br />
The following test parameters<br />
should be recorded.<br />
• axial load (P);<br />
• confining pressure (a22 = 033);<br />
107
• vertical displacement of the specimen (/_v);<br />
• radial displacement of the specimen (tSh);<br />
The following engineering<br />
quantities should be calculated.<br />
• 0.11= P/A + confining stress (022 _--- 0"33); axial stress where A is the<br />
cross-sectional area of the specimen<br />
• Ell= tSv/h;uniaxial strain where h is the height of the specimen<br />
5.3 Frequency Sweep Test<br />
5.3.1 Specimen Setup--Attach vertical and horizontal LVDTs to the specimen as<br />
shown in figure 4. The vertical LVDT is used to measure changes in specimen height as<br />
represented by changes in the distance between the top and bottom platens. The horizontal<br />
LVDTs measure the difference in horizontal displacement between two points on the<br />
specimen separated by 37.5 mm. The horizontal LVDTs should be mounted such that they<br />
contact the specimen at approximately 19 mm on either side of the specimen at mid-height.<br />
Position the vertical test system head to allow the specimen-platen assembly to slide between<br />
the bottom horizontal and top vertical heads. Position the horizontal test head such that the<br />
top and bottom test heads are aligned vertically. Slide the specimen between the heads so that<br />
it is centered between the heads. Secure the platens to the heads by activating the hydraulic<br />
clamps.<br />
Completely lower the environmental chamber to seal off the specimen from the outside<br />
temperature influences. Testing is conducted at temperatures of 4°C, 20°C, and 40°C.<br />
5.3.2 Testing--The test is conducted at constant height requiring the vertical actuator<br />
servovalve to be controlled by the vertical LVDT. Furthermore, this is a strain-controlled<br />
test with the maximum shear strain limited to 0.0001 mm/mm. Precondition the specimen by<br />
applying a sinusoidal horizontal shear strain of amplitude = 0.0001 mm/mm at a frequency<br />
of 10 Hz for 100 cycles. After preconditioning, a series of 10 tests are conducted in<br />
descending order of frequency at each temperature level beginning with the lowest<br />
temperature. (The shear strain is applied at the following frequencies at each test<br />
temperature: 10, 5, 2, 1, 0.5, 0.2, 0.1, 0.05, 0.02 and 0.01 Hz.) Recording 50 data points<br />
per load cycle is sufficient. Since the test is conducted at a constant height, the axial actuator<br />
is under closed loop feedback control from the LVDT measuring the relative displacement<br />
between the specimen caps.<br />
The following test parameters<br />
should be recorded.<br />
• axial load (P);<br />
• shear load (V);<br />
• div = vertical displacement of the specimen<br />
• t5h = horizontal displacement of the specimen<br />
108
The following engineering<br />
quantities should be calculated.<br />
• 011 = P/A; axial stress where A is the cross-sectional area of the specimen<br />
• "/'12= V/A; shear stress<br />
• _12 = 6J2h; shear strain where h is the height of the specimen<br />
• G = T12/e12; complex shear modulus;<br />
• _k = phase angle in degrees<br />
5.4 Simple Shear Test (Constant Height)<br />
5.4.1 Specimen Setup--Attach vertical and horizontal LVDTs to the specimen as<br />
shown in figure 4. The vertical LVDT is used to measure changes in specimen height as<br />
represented by changes in the distance between the top and bottom platens. The horizontal<br />
LVDTs measure the difference in horizontal displacement between two points on the<br />
specimen separated by 37.5 mm. The horizontal LVDTs should be mounted such that they<br />
contact the specimen at approximately. 19 mm on either side of the specimen at mid-height.<br />
Position the vertical test system head to allow the specimen-platen assembly to slide between<br />
the bottom (horizontal) and top (vertical) heads. Position the horizontal test head such that<br />
the top and bottom test heads are aligned vertically. Slide the specimen between the heads so<br />
that it is centered between the heads. Secure the platens to the heads by activating the<br />
hydraulic clamps.<br />
Completely lower the environmental chamber to seal off the specimen from the outside<br />
temperature influences. Testing is conducted at a temperatures of 4°C, 20°C, and 40°C.<br />
5.4.2 Testing--This is a stress-controlled test with the feedback to the horizontal<br />
actuator servovalve from the magnitude of the shear load. The test is conducted at constant<br />
height, requiring the vertical actuator servovalve to be controlled by the vertical LVDT.<br />
(i.e., the axial actuator is under closed loop feedback control from the LVDT to measure the<br />
relative displacement between the specimen caps.) Precondition the specimen by applying a<br />
7 kPa shear stress for 100 cycles. After preconditioning the specimen, increase the shear<br />
stress at a rate of 70 kPa/s and hold for 10 seconds in accordance with figure 7 (35, 105, and<br />
350 kPa at 40, 20 and 4°C, respectively). After 10 seconds, reduce the shear stress to zero<br />
at a rate of about 21 kPa/s. Continue to record data for an additional 30 seconds during this<br />
recovery period. Axial and shear deformations, as well as axial and shear loads, should be<br />
recorded at appropriate intervals during the test, i.e., approximately 10 data points per<br />
second.<br />
The following test parameters<br />
should be recorded.<br />
• axial load (P);<br />
• shear load (V);<br />
• _5v = vertical displacement of the specimen<br />
• t_h = horizontal displacement of the specimen<br />
109
The following engineering<br />
quantities should be calculated.<br />
• all= P/A; axial stress where A is the cross-sectional area of the specimen<br />
• 712 = V/A; shear stress<br />
• e12 = 5dh; shear strain where h is the height of the specimen<br />
5.5 Repetitive Shear Test (Constant Stress Ratio)<br />
5.5.1 Specimen Setup--Attach vertical and horizontal LVDTs to the specimen as<br />
shown in figure 4. The vertical LVDT is used to measure changes in specimen height as<br />
represented by changes in the distance between the top and bottom platens. The horizontal<br />
LVDTs measure the difference in horizontal displacement between two points on the<br />
specimen separated by 37.5 mm. The horizontal LVDTs should be mounted such that they<br />
contact the specimen at approximately 19 mm on either side of the specimen at mid-height.<br />
Position the vertical test system head to allow the specimen/platen assembly to slide between<br />
the bottom (horizontal) and top (vertical) heads. Position the horizontal test head such that<br />
the top and bottom test heads are aligned vertically. Slide the specimen between the heads so<br />
that it is centered between the heads. Secure the platens to the heads by activating the<br />
hydraulic clamps.<br />
Completely lower the environmental chamber to seal off the specimen from the outside<br />
temperature. This stress-controlled test is usually performed at an effective temperature for<br />
permanent deformation (see The SUPERPAVE ® Mix Design Manual for New Construction<br />
and Overlays, chapter 4), calculated from weather data for the site of the paving project.<br />
5.5.2 Testing--This is a constant stress ratio test. The vertical actuator servovalve is<br />
controlled by the magnitude of axial load as feedback. The horizontal actuator servovalve is<br />
controlled by the magnitude of shear load as feedback. Both axial and shear loads are<br />
haversine in shape and are applied such that, at every moment in time during the loading<br />
phase, the ratio of axial load to shear load remains constant. Precondition the specimen by<br />
applying 100 cycles of synchronized haversine axial and shear load pulses (0.1 second on<br />
and 0.6 seconds off). The axial stress for preconditioning should not exceed 7 kPa with the<br />
ratio of axial to shear stress held constant at a value of 1.2 to 1.5. After preconditioning, the<br />
synchronized haversine axial and shear stress pulses should be applied for a total of 5000<br />
repetitions or until 5 % shear strain is reached. During testing the ratio of axial to shear stress<br />
should be held constant at a value of 1.2 to 1.5. The maximum shear stress level should be<br />
determined in accordance with the guidelines in table 1. Axial and shear deformations, as<br />
well as axial and shear loads, should be recorded at appropriate intervals. Collecting 60 data<br />
points per load cycle is sufficient.<br />
The following test parameters<br />
should be recorded.<br />
• axial load (P)<br />
• shear load (V)<br />
• ratio of axial to shear load<br />
110
Table 1. Guidelines for Shear and Compressive Stress<br />
Base Maximum Shear (r) and Compressive (or)<br />
Condition Stress Levels (kPa) at Asphalt Binder Content<br />
Above Design At Design Below Design<br />
r tr_ r _, r tr_<br />
Weak 84 119 63 98 49 56<br />
Strong 98 175 84 105 56 91<br />
Note: A weak base is defined as an unbound granular or crushed stone material (i.e., new construction), whereas<br />
a strong base is defined as an existing asphalt concrete or portland cement concrete pavement, a cement-stabilized<br />
or asphalt-stabilized base, or a strong crushed stone base material (i.e., a resilient modulus of 560,000 kPa or<br />
greater).<br />
• t5v = vertical displacement of the specimen<br />
• t5h = horizontal displacement of the specimen<br />
The following engineering<br />
quantities should be calculated.<br />
• an = P/A; axial stress where A is the cross-sectional area of the specimen<br />
• 7"12= V/A; shear stress<br />
• _12 = tSJh; shear strain where h is the height of the specimen<br />
5.6 Repetitive Shear Test (Constant HeighO<br />
5.6.1 Specimen Setup--Attach vertical and horizontal LVDTs to the specimen as<br />
shown in figure 4. The vertical LVDT is used to measure changes in specimen height as<br />
represented by changes in the distance between the top and bottom platens. The horizontal<br />
LVDTs measure the difference in horizontal displacement between two points on the<br />
specimen separated by 37.5 mm. The horizontal LVDTs should be mounted such that they<br />
contact the specimen at approximately 19 mm on either side of the specimen at mid-height.<br />
Position the vertical test system head to allow the specimen-platen assembly to slide between<br />
the bottom horizontal and top vertical heads. Position the horizontal test head such that the<br />
top and bottom test heads are aligned vertically. Slide the specimen between the heads so that<br />
it is centered between the heads. Secure the platens to the heads by activating the hydraulic<br />
clamps.<br />
Completely lower the environmental chamber to seal off the specimen from the outside<br />
temperature influences. Testing is conducted at the seven-day maximum pavement<br />
temperature occuring at 50 mm depth.<br />
5.6.2 Testing--This is a stress-controlled test with the feedback to the horizontal<br />
actuator servovalve from the magnitude of the shear load. The test is conducted at constant<br />
height requiring the vertical actuator servovalve to be controlled by the vertical LVDT (i.e.,<br />
111
the axial actuator is under closed loop feedback control from the LVDT measuring the<br />
relative displacement between the specimen caps). Precondition the specimen by applying a<br />
haversine load corresponding to a 7 kPa shear stress for 100 cycles (0.1 s on, 0.6 s off).<br />
After preconditioning the specimen, apply a 70 kPa haversine shear pulse (0.1 s on and 0.6 s<br />
off) for 5000 cycles or until 5 % shear strain is reached. Axial and shear deformations, as<br />
well as axial and shear loads, should be recorded at appropriate intervals. Collecting 60 data<br />
points per load cycle is sufficient.<br />
The following test parameters<br />
should be recorded.<br />
• axial load (P)<br />
• shear load (1/)<br />
• dtv= vertical displacement of the specimen<br />
• c5h = horizontal displacement of the specimen<br />
The following engineering quantities should be calculated.<br />
• all= P/A; axial stress where A is the cross-sectional area of the specimen<br />
• r12 = V/A; shear stress<br />
• e12 = /iJh; shear strain where h is the height of the specimen<br />
112
SIDE<br />
VIEW<br />
(this side fixed<br />
Reaction<br />
to prevent<br />
horizontal movement) "" f 1<br />
Accumulated ,' Specimen ,'<br />
Load (to maintain constant specimen height)<br />
$<br />
Platen<br />
Shear '_"_ "
Figure 2. Platen-Specimen<br />
Assembly Device<br />
114
Figure 3. Application<br />
of Elastic Membrane and O-rings<br />
115
Figure 4. Positioning of Vertical and Horizontal LVDTs (Radial LVDT not shown)<br />
116
150<br />
o TENP = 4C<br />
-- I?0 o o A TEMP -- POC<br />
°<br />
o_<br />
/ \<br />
[] TEMP = 4OC<br />
,,, go<br />
I---<br />
---D<br />
[ofJ3 ....... "_i<br />
z 60<br />
H<br />
Z<br />
H<br />
U_<br />
Z<br />
o 30<br />
\\<br />
OD ' ' ' ,'LI ....[_....e, ,[] z_ o ,<br />
1] 10 20 30 40 50 60 71] 81] 91] 1111]<br />
TIME.<br />
seconds<br />
Figure 5. Loading for Volumetric/Hydrostatic<br />
Test<br />
117
tO0<br />
© ©<br />
....... OT...=.c<br />
on A TEMP = 20C<br />
U_<br />
_ / []TEMP = 40C<br />
" 60<br />
m 40<br />
H<br />
x<br />
80<br />
N_ __0 A 0,<br />
0 20 40 60 80 100<br />
TIME. seconds<br />
Figure 6. Loading for Uniaxial Strain Test<br />
118
6O<br />
o TEMP = 4C<br />
50 []............. O A TEIVlp = 2OC<br />
\<br />
-- k [] TEHP = 4OC<br />
40<br />
\\<br />
III \ '<br />
_ 30 ,/ \_ ',..Oe,.<br />
8:0 I o ',<br />
7- I _ '<br />
f ",<br />
10 / , ,<br />
¢ o, ,,<br />
Oo , o--L , e ......a _............ []<br />
0 l0 20 30 40 50<br />
TIPIE,<br />
\<br />
seconds<br />
Figure 7. Loading for Simple Shear (Constant Height Test)<br />
119
Standard Method of Test for<br />
Determining the Creep Compliance and Strength<br />
of Modified and Unmodified Hot Mix Asphalt Using<br />
Indirect Tensile Loading Techniques<br />
<strong>SHRP</strong> Designation: M-0051<br />
I. SCOPE<br />
1.1 This method covers the determination of creep compliance and strength at<br />
different loading times using diametral loadings (commonly referred to as indirect tensile<br />
testing) for compacted, dense-graded, hot-mixed, hot-laid bituminous mixtures. Indirect<br />
tensile testing is used to characterize asphalt concrete mixtures in tension for thermal and<br />
fatigue cracking analyses.<br />
1.2 The indirect tensile creep and failure tests are intended for low-temperature<br />
characterization (0°C and below) of cylindrical laboratory compacted and/or field-cored<br />
asphalt concrete specimens. The primary goal of the test method is to determine the master<br />
compliance curve and failure limits (strength, strain or energy) as a function of temperature,<br />
which are required inputs into a mechanistic-based low temperature cracking performance<br />
prediction model.<br />
1.3 The test method also provides strength information and data required at<br />
temperatures less than 20°C to estimate the number of loading cycles to propagate a crack<br />
through an asphalt concrete layer in fatigue cracking predictions that use fracture mechanics.<br />
1.4 This method is applicable to dense-graded, hot-mixed, hot-laid asphalt concrete<br />
mixtures, as defined by ASTM D 3515 (Bituminous Paving Mixtures, Hot-Mix, Hot-Laid),<br />
and may be used on cores recovered from roadways or cylindrical specimens compacted in<br />
the laboratory.<br />
1.5 The values of creep compliance and tensile strength determined with this method<br />
can be used in linear-elastic and non-linear elastic layered system theories to calculate the<br />
low temperature and fatigue cracking potential of asphalt concrete layers subjected to thermal<br />
and wheel loadings.<br />
1.6 The values stated in SI units are to be regarded as the standard.<br />
_Thisstandardis basedon <strong>SHRP</strong>Product 1022.<br />
121
1.7 This test may involve hazardous materials, operations, and equipment. This<br />
standard does not purport to address all of the safety problems associated with its use. It is<br />
the responsibility of the user of this standard to establish appropriate safety and health<br />
practices and determine the applicability of regulatory limitations prior to use.<br />
2. APPLICABLE DOCUMENTS<br />
2.1 <strong>SHRP</strong> Documents<br />
M-002 Preparation of Compacted Specimens of Modified and Unmodified Hot Mix Asphalt<br />
by Means of the <strong>SHRP</strong> Gyratory Compactor<br />
2.2 AASHTO Documents<br />
T166 Bulk Specific Gravity of Compacted Bituminous Mixtures<br />
T209 Maximum Specific Gravity of Bituminous Paving Mixtures<br />
T245 Test Method for Resistance to Plastic Flow of a Bituminous Mixture Using the<br />
Marshall Apparatus<br />
T247 Method for Preparation of Test Specimens of a Bituminous Mixture by Means of the<br />
California Kneading Compactor<br />
T269 Percent Air Voids in Compacted Dense and Open Bituminous Paving Mixtures<br />
T275 Standard Method of Test for Bulk Specific Gravity of Compacted Bituminous Mixes<br />
Using Paraffin-Coated Specimens<br />
2.3 ASTM Documents<br />
D3202 Preparation of Bituminous Mixture Beam Specimens by Means of the California<br />
Kneading Compactor<br />
D3387 Test for Compaction and Shear Properties of Bituminous Mixtures by Means of the<br />
U.S. Corps of Engineers Gyratory Testing Machine (GTM)<br />
D3515 Specifications for Hot-Mixed, Hot-Laid Bituminous Paving Mixtures<br />
D4013 Preparation of Test Specimens of Bituminous Mixtures by Means of Gyratory Shear<br />
Compactor<br />
122
3. SUMMARY OF METHOD<br />
3.1 This test method consists of two types of tests: a tensile creep test and a tensile<br />
strength test. The tensile strength test can be performed separately (for fatigue cracking<br />
analyses) or in concert with the creep test (for thermal cracking analyses).<br />
3.2 A static load of fixed magnitude is applied along the diametral axis of a<br />
preconditioned specimen for a fixed duration of time, 1,000 seconds. The horizontal and<br />
vertical deformations measured near the center of the specimen are used to calculate a tensile<br />
compliance at a particular duration of time. Loads are selected to keep strains in the linear<br />
viscoelastic range (typically below 300 microstrains). By measuring both horizontal and<br />
vertical strains in regions where the stresses are relatively constant and away from the<br />
localized non-linear effects induced by the steel loading strips, the Poisson's ratio can be<br />
more accurately determined. The Poisson's ratio is then used to better predict threedimensional<br />
stresses and strains.<br />
3.3 The failure portion of the test immediately follows the creep portion. Without<br />
releasing the creep load, a constant rate of vertical deformation (or ram movement) is applied<br />
to the specimen to failure. The failure limits determined can be input into mechanistic-based<br />
models for thermal cracking or used to compare relative qualities of mixtures. The failure<br />
portion of the test method can be performed separately when only the tensile strength<br />
properties are needed.<br />
4. DEFINITIONS<br />
4.1 Creep Compliance--The slow movement of asphalt concrete mixtures under a<br />
sustained load per unit of the applied stress; time-dependent strain (continuing strain) with a<br />
sustained stress level.<br />
5. SIGNIFICANCE AND USE<br />
5.1 The values of creep compliance can be used to evaluate the relative quality of<br />
materials, as well as to generate input for pavement design and evaluation models. From<br />
creep testing, these values include the intercept and straight line slope of log creepcompliance<br />
versus log loading time, or the entire master-compliance curve. The test can be<br />
used to study effects of temperature, load magnitude, binder content, and loading time.<br />
5.2 When used in conjunction with other mixture physical properties, the creep<br />
compliance may contribute to the overall mixture characterization. It is one factor for<br />
determining a mixture's suitability for use as a highway paving material under given traffic<br />
and environmental conditions.<br />
5.3 Reheated, recompacted mixtures may be used in this method, but the resulting<br />
creep compliance values will be higher than for newly prepared mixtures because of changes<br />
123
in binder viscosity, an important factor of creep strains, as measured under these specific<br />
loading conditions and temperatures.<br />
6. APPARATUS<br />
6.1 Axial Loading Machine--Any loading machine capable of providing a fixed or<br />
constant load and constant rate of ram displacement with a resolution of + 4.5 N shall be<br />
used. Typically, a closed-looped electrohydraulic system, or a combination of a screw-type<br />
machine with a cam and switch or timer control of solenoid valves that operates a pneumatic<br />
air piston can be used.<br />
6.2 Temperature System--The temperature control system shall be capable of<br />
control over a temperature range from -20 to 20°C 5: 0.5°C of the specified temperature<br />
within the range (see note 1). The system can be a room, chamber or cabinet that shall be<br />
large enough to hold at least three specimens for a period of 12 hours prior to testing. If the<br />
testing machine is located in a room without the specified temperature control systems, a<br />
controlled temperature cabinet shall be used during the entire test.<br />
NOTE 1.--Use<br />
of the indirect tensile test to characterize mixtures in tension at relatively high temperatures<br />
(above room temperature) has been a problem, at long loading times (i.e., creep testing). As most asphalt concrete<br />
mixes are far from elastic at high temperatures, these equations must be used with caution. The indirect tensile<br />
equations used to calculate the tensile strains and moduli values were developed using the theory of elasticity. Thus,<br />
the test temperature of the IDT creep test should be 0°C or less, and the test temperature of the IDT strength test<br />
should be less than 20°C.<br />
6.3 Specimen Deformation Measurement Devices--The creep compliance test requires<br />
deformation transdfacers with a high resolution and small range during the creep portion of<br />
the test and less resolution but a larger range during the strength portion of the test. The<br />
linear variable differential transducer (LVDT) is considered to be the most suitable<br />
deformation transducer for the test. A range of + 0.25 mm is required, while simultaneously<br />
maintaining a minimum resolution of 2.5 x 10-4 mm.<br />
6.4 Specimen Load Measurement Device--The load measuring device is to be an<br />
electronic load cell. The load is to be measured by placing the load cell between the loading<br />
platen and piston. The total load capacity of the load transducer (load cell) shall be of the<br />
proper order of magnitude with respect to the maximum total load to be applied to the test<br />
specimen. Generally, its capacity should be no greater than 5 times the total maximum load<br />
applied to the test specimen to ensure that the necessary measurement accuracy is achieved.<br />
The load-measuring device shall be capable of measuring the load to an accuracy of + 1% of<br />
the applied load.<br />
6.5 Recording Device--Specimen behavior in the creep compliance test is evaluated<br />
from time records of applied load and specimen deformation. Commonly, these parameters<br />
are recorded on a multichannel strip-chart recorder. Analog-to-digital data acquisition<br />
systems may be used if the data can be converted into a convenient form for analysis and<br />
interpretation.<br />
124
6.5.1 For analog strip-chart recording equipment, the deformation recorder trace<br />
must be of sufficient magnitude and time resolution to enable accurate data reduction.<br />
Resolution of each variable should be better than 2 % of the maximum value being measured.<br />
The trace shall have sufficient contrast to the background so that it may be reproduced in<br />
reports. At all times, the minimum resolution of the trace must be maintained at 2% of the<br />
maximum value of the recorded parameter.<br />
6.5.2 For digital data acquisition systems, the minimum sampling frequencies for the<br />
1,000-second creep test are as follows:<br />
• 100 Hz for the first 10 seconds<br />
• 1 Hz for the next 5 minutes (up to 300 seconds)<br />
• 0.2 Hz through the remainder of the test (remaining 700 seconds)<br />
For the indirect tensile strength test, which is performed immediately after the creep<br />
test and uses a stroke rate of 13 mm per minute, a sampling frequency of 20 Hz is used<br />
through the entire test (see note 2).<br />
NOTE 2.--Experience has shown that a 16-bit A/D board is required to obtain both the resolution needed in<br />
the creep test and the range for the strength portion.<br />
6.5.3 When a digital data acquisition system is used, a special conditioner is<br />
required. This special conditioner shall have the following characteristics.<br />
• An excitation frequency of 2.9 to 20 kHz<br />
• An excitation voltage of 1 V<br />
• A load independence of 30 ohms<br />
• An output + 10 V<br />
• A noise level less than 2.5 × 10-4 mm measured at output of the conditioner when<br />
+ 10 V equals + 2.5 mm<br />
• A filter cut-off greater than 5 Hz<br />
6.6 Oven--The oven for the preparation of hot mixtures shall be capable of being set<br />
to maintain any desired temperature from room temperature to 163°C.<br />
6.7 Mounting Template--A mounting template, as shown in figure 1, is used to place<br />
and mount the eight brass gauge points to each side of the test specimen (four per side).<br />
6.8 Specimen Loading Frame--The specimen load frame shall be capable of<br />
delivering test loads in good alignment and with minimal friction (less than 2.27 kg<br />
resistance) in guides or bearings even when eccentric loads occur (caused by slightly uneven<br />
specimens, temperature changes, etc.) (see note 3). Loading platens shall have a width equal<br />
to D/8, where D is the standard diameter of the test specimens, and a radius of r -- D/2.<br />
NOTE3.--Often a smaller guide frame with special alignment capabilities is used in conjunction with the<br />
larger loading flame to accomplish this, as portrayed in figure 2.<br />
125
7. PREPARATION OF TEST SPECIMENS<br />
7.1 Laboratory Molded Specimens<br />
7.1.1 Prepare three replicate laboratory-molded specimens, as a minimum for each<br />
test temperature, in accordance with <strong>SHRP</strong> test method M-002 or other acceptable<br />
procedures, such as AASHTO T247 or ASTM D3387 and D4013 (see notes 4 and 5). Other<br />
procedures include cores cut from laboratory-prepared beams or slabs. If only strength<br />
measurements are required, the number of specimens can be reduced to two per temperature.<br />
NOTE 4.--The type of compaction device will influence the test results or creep compliance values.<br />
<strong>SHRP</strong> M-002 is the preferred technique, but AASHTO T247 produces specimens that are reasonable.<br />
AASHTO T245 (Marshall hammer) is not permitted for preparing specimens for creep compliance testing.<br />
NOTE 5.--Test specimens normally are compacted using a standard compactive effort. A specific<br />
compactive effort, however, may not reproduce the air voids measured on field cores. If specimens are to be<br />
compacted to a target air void content, the compactive effort needs to be varied. For <strong>SHRP</strong> M-002, the number of<br />
gyrations can be varied; for AASHTO T247 (kneading compactor) the number of tamps, the foot pressure and/or the<br />
leveling load can be altered. The actual compactive effort to be used should be determined experimentally.<br />
7.1.2 Saw at least 6 mm from both sides of each test specimen to provide smooth,<br />
parallel (saw-cut) surfaces for mounting of measurement gauges (see note 6). The final height<br />
and diameter of the sawed laboratory molded specimens are given under section 7.3.<br />
NOTE6.--Measurements taken on cut faces yield more consistent results, and gauge points can be epoxied<br />
with much greater bonding strength.<br />
7.2 Core Specimens<br />
7.2.1 Cores shall have smooth and parallel surfaces and conform to the height and<br />
diameter requirements specified for specimens under section 7.3. Three replicate cores shall<br />
be prepared for each test temperature. If only strength measurements are required, the<br />
number of cores can be reduced to two per temperature. If rough or uneven surfaces exist,<br />
cores shall be sawn to provide required smoothness and conformity, as required in section<br />
7.1.2 (see note 6).<br />
7.3 Specimen Size<br />
7.3.1 Indirect tensile specimens to be tested shall have a height (or thickness) of at<br />
least 30 mm and a minimum diameter of 100 mm for mixtures that contain a maximum<br />
aggregate size of 25 mm or less. Mixtures that contain maximum size aggregates up to<br />
38 mm in diameter shall have a height of at least 50 mm and a minimum diameter of<br />
150 mm. The specimen height-to-diameter ratio shall exceed 0.33 (see note 7).<br />
NOTE 7.--The size of test specimens has an influence on results from the tensile creep compliance test. If at<br />
all possible, the ratio of the sample diameter to the maximum aggregate size diameter should be greater than 4.<br />
126
8. PROCEDURE<br />
8.1 Measure the bulk specific gravity of each test specimen in accordance with<br />
AASHTO T166 or T275, whichever applies (note 8).<br />
NOTE 8.--If the bulk specific gravity of the test specimens is measured in accordance with AASHTO T166,<br />
the specimens must be allowed to dry prior to testing and preconditioning. Moisture or water trapped in the<br />
permeable voids can have an effect on the test results. Retaining the specimens in the temperature cabinet for<br />
12 hours should be sufficient to allow the moisture to evaporate from the permeable voids.<br />
8.2 After the specimens become dry, place the test specimen in a controlled<br />
temperature cabinet and bring it to the specified test temperature. Unless the temperature is<br />
monitored and the actual temperature known, the specimen shall remain in the cabinet at the<br />
specified test temperature for at least 12 hours prior to testing.<br />
8.3 Measure the height and diameter of the specimen to the nearest 2.5 mm. Height<br />
or thickness and diameter measurements shall be made at 1/3 points and the values averaged<br />
for use in any calculations.<br />
8.4 Mounting LVDTs on the Specimen's Surface<br />
8.4.1 Transducers shall be mounted about the center of fiat faces of diametral<br />
specimens, with a gauge length equal to one-fourth the specimen's diameter. They should be<br />
mounted so that the transducer's centerline is no more than 6 mm above the specimen's<br />
surface. Measurements shall be taken in both horizontal and vertical directions on both sides<br />
of the specimen.<br />
8.4.2 One such system that has been used successfully is shown in figure 3. The<br />
displayed system uses a brass mounting apparatus clamped onto brass gauge points. The<br />
gauge points are 8 mm in diameter by 3 mm thick and are placed on the specimen with<br />
epoxy and a specially designed gauge point template (see figure 3 and note 9). One piece of<br />
the mounting apparatus holds the LVDT's transformer securely, while the other piece<br />
suspends the core of the LVDT. Both pieces clamp securely to the gauge points with set<br />
screws.<br />
NoTE 9.--The two-piece mounting apparatus shown in figure 3 was designed to be used with sub-miniature<br />
LVDTs and is machined from a 12-mm diameter brass rod.<br />
8.5 Precondition the room-temperature specimens by one of the following procedures<br />
for different equipment.<br />
8.5.1 For a closed-looped electrohydraulic system. Apply 100 cycles of haversine<br />
load with amplitude equivalent to 70 kPa tension. One load cycle shall consist of 0.1 seconds<br />
of haversine loading and 0.9 seconds of zero-load condition. The amplitude of the load may<br />
be calculated by<br />
P = 11 ×<br />
104tD<br />
127
where<br />
t = specimen thickness, m (see section 8.3)<br />
D = specimen diameter, m (see section 8.3)<br />
8.5.2 For a combination of a screw-type machine with a cam and switch operating a<br />
pneumatic air piston. Apply a constant load equivalent to 70 kPa in tension for 10 seconds.<br />
After 10 seconds, release the entire preconditioning load.<br />
8.6 Following the preconditioning procedure, the temperature of the environmental<br />
chamber or room is lowered to the test temperature, and the specimens shall be held at the<br />
test temperature for 12 hours prior to testing, unless the temperature is monitored within a<br />
similar specimen. The remainder of the test procedure is divided into two parts. The first is<br />
for the creep-strength test procedure required for thermal cracking evaluations, and the<br />
second is for only the strength test procedure required for obtaining data for fatigue cracking<br />
analyses.<br />
8.7 Creep-Strength Testing Procedures, Thermal Cracking<br />
8.7.1 The test temperatures for the creep-strength test to evaluate an asphalt concrete<br />
mixture's resistance to thermal cracks are 0°C and less. Three test temperatures are typically<br />
required for calculating a master compliance curve: 0, -10, and -20°C. As a minimum,<br />
however, at least two test temperatures are required for use. Typical values that have been<br />
used and proven to produce acceptable results are -5<br />
and -15°C.<br />
8.7.2 After maintaining a constant test temperature in the test specimens for the<br />
proper amount of time, zero or rebalance the electronic measuring system and apply a static<br />
load of fixed magnitude (+ 2%) without impact to the specimen.<br />
8.7.3 The fixed load to be used for tensile creep portion of the test must produce<br />
between 50 and 200 microstrains of horizontal strain in the first 60 seconds of testing. If<br />
either limit is violated, the test shall be stopped and the load adjusted accordingly. A<br />
minimum recovery time of 3 minutes is required before restarting the test. Strict compliance<br />
to these limits will prevent both non-linear response characterized by exceeding the upper<br />
limit and minimize problems associated with noise and drift inherent in sensors when<br />
violating the lower strain limit.<br />
8.7.4 Monitor both of the vertical and horizontal deformations on both sides of the<br />
specimen during the entire loading time. The load shall be applied for a period of 1,000<br />
seconds + 15 seconds.<br />
NOTE 10.--Shorter loading times and rest periods (section 8.7.4) can be used to determine the creep<br />
properties of asphalt concrete mixtures. It is important that the slope of the log of time versus log of creep<br />
compliance be constant or in the steady state range.<br />
8.7.5 After the fixed load has been applied over a period of 1,000 seconds,<br />
additional load shall be applied to the specimen at a rate of 12.5 mm of ram or vertical<br />
128
movement per minute. Both the horizontal and vertical movements and load shall be<br />
monitored, until the load begins to decrease (10% reduction from the peak value).<br />
8.8 Strength Testing Procedure, Fatigue Cracking<br />
20°C.<br />
8.8.1 The test temperature to be used for fatigue cracking analyses shall not exceed<br />
8.8.2 After maintaining a constant temperature in the test specimens for the proper<br />
amount of time, zero or rebalance the electronic measuring system.<br />
8.8.3 Apply a load to the specimen at a rate of 50 mm of ram or vertical movement<br />
per minute. Both the horizontal and vertical movements and load shall be monitored, until<br />
the load begins to decrease. The test should be stopped as soon as the load begins to decrease<br />
to prevent damage to the LVDT equipment from a sudden failure within the specimen.<br />
8.9 After testing has been completed, the specimens shall be broken down and the<br />
maximum specific gravity measured in accordance with AASHTO T209.<br />
9. CALCULATIONS<br />
T269.<br />
9.1 Calculate the air voids for each test specimen in accordance with AASHTO<br />
9.2 Compliance Calculations<br />
9.2.1 Normalize all vertical and horizontal deformation measurements to account for<br />
differences caused by variations between specimens in thickness, diameter and applied load.<br />
These normalized deformations are calculated by:<br />
A n = Am, i<br />
ti Pavg Di<br />
t,vg P, O,,g<br />
where<br />
A n ----- Normalized deformation in the horizontal or vertical direction<br />
Am, i "- Actual measured deformation in the horizontal or vertical<br />
direction for specimen i.<br />
ti, Di, Pi = Average thickness, diameter, and load, respectively, for<br />
specimen i at a specific temperature.<br />
tavg, Davg, Pavg = Average thickness, diameter, and applied load, respectively, for<br />
all specimens tested at a specific temperature.<br />
129
9.2.2 Calculate the average vertical and horizontal displacements with time using the<br />
trimmed mean approach. In other words, the highest and lowest normalized deformation<br />
readings in the vertical and horizontal directions are excluded from calculating the average<br />
values. The highest and lowest readings are identified by comparing the deformations<br />
between 460 and 540 seconds of loading time. For each of these specimens at one<br />
temperature, a normalized vertical and horizontal displacement with time is calculated.<br />
9.2.3 Calculate the average ratio between the horizontal and vertical readings with<br />
time, which is related to Poisson's ratio, v.<br />
specimen.<br />
9.2.4 Calculate the corrected tensile and compressive stresses in the center of the<br />
Ox = 11;tavg 2Pavg O avgj]Cox<br />
6 Pavg ] Coy<br />
= ;.v-, oh,,]<br />
where<br />
C_, C_y = Correction factors for the horizontal and vertical stresses,<br />
respectively, from table 1.<br />
9.2.5 Calculate the revised Poisson's ratio, v*<br />
1.093 CBx I<br />
V* =<br />
1.093 CBx ]<br />
o,- o,<br />
where<br />
CBr, CBx = Correction factors for bulging in the vertical and horizontal<br />
directions, respectively, from table 2<br />
9.2.6 Subtract the initial _,from the revised v*<br />
E -- v* - v<br />
130
If E is greater than 0.01, substitute v* for v and repeat steps 10.1.4 through 10.1.6. If<br />
E is less than or equal to 0.01, proceed with the following steps.<br />
9.2.7 Calculate the tensile strain in the center of the specimen.<br />
where:<br />
l = gauge length (25.4 or 38.1 mm)<br />
9.2.8 Calculate the compliance at any time, D(t).<br />
D(t) -<br />
Ex<br />
(I x - V*(I Y<br />
9.3 Tensile Strength Calculations<br />
9.3.1 Plot the normalized vertical displacement minus the normalized horizontal<br />
displacement as a function of time.<br />
A* = Ay -A x<br />
9.3.2 DcfincthetimeatwhichA* peakson oneofthespccimcn'sfaccs.Calculate<br />
thetensile strcssattha time.Thistensile stressisthcstrength ofthemix.<br />
(It=<br />
ax@ tf_l<br />
10. REPORT<br />
10.1 Thc rcportshallincludcthefollowinginformation as a minimum.<br />
10.1.1Thc bulkspccific gravityofeachspecimentested.<br />
10.1.2The maximum spccific gravityoftheasphaltconcrctcmixture.<br />
10.1.3The heightanddiarnctcr ofalltestspecimens.<br />
10.1.4The tcstcmperaturc andloadlevels(forcreeptesting) usedduringthetest.<br />
10.1.5The creepcomplianccvaluesforthetimesspccificd, as a minimum.<br />
131
10.1.6 The slope of the creep-compliance curve at each test temperature.<br />
10.1.7 The indirect tensile strength and failure strain of the mixture.<br />
132
Table 1. Correction Factors for Horizontal and Vertical Stress<br />
Diameter to Thickness Ratio, (t/D)<br />
D = 100 mm or 150 p 0.167 0.333 0.500 0.625 0.750<br />
mm<br />
C,_ 0.20 0.9471 0.9773 1.0251 1.0696 1.1040<br />
0.35 0.9561 1.0007 1.0871 1.1682 1.2321<br />
0.45 0.9597 1.0087 1.1213 1.2307 1.3171<br />
C,y 0.20 -0.9648 -0.9754 -0.9743 -0.9693 -0.9611<br />
0.35 -0.9732 -0.9888 -0.9844 -0.9710 -0.9538<br />
0.45 -0.9788 -0.9971 -0.9864 -0.9646 -0.9395<br />
Table 2. Bulging Correction<br />
Factors<br />
Diameter to Thickness Ratio, (t/D)<br />
D = 100 mm or 1, 0.167 0.333 0.500 0.625 0.750<br />
150 mm<br />
Csx 0.20 0.9816 0.9638 0.9461 0.9358 0.9294<br />
0.35 0.9751 0.9518 0.9299 0.9179 0.9108<br />
0.45 0.9722 0.9466 0.9234 0.9111 0.9040<br />
CBr 0.20 0.9886 0.9748 0.9677 0.9674 0.9688<br />
0.35 0.9808 0.9588 0.9479 0.9473 0.9493<br />
0.45 0.9759 0.9492 0.9364 0.9358 0.9380<br />
133
14" X 112" X 1/16"<br />
BACKING PLATE<br />
/ \ / \ ffYP.)<br />
/ /_)// 1" C. TO C. \ \<br />
\ \<br />
I/2"<br />
1.5" TO C.<br />
0.315" /<br />
\ \ SQUARE / \ (_//<br />
\ / HOLE "/<br />
(TYP.)<br />
2" RAD.<br />
3/10" x 3/10" x 1/1 6"<br />
BACKING PLATE<br />
_1/6"<br />
x 1/4" SLOT<br />
(TYP.)<br />
Figure 1. Four-Inch Gauge Point Template (Top View)<br />
134
Figure 2. Specimen<br />
Loading Frame with Smaller Guide Frame<br />
135
1/1 6" O.D. 0-80 x 1/4" LVDT<br />
BRASS TUBE CLAMP SCREW COIL ASSEMBLY<br />
CORE ASSEMBLY _ _ S<br />
"_',,_ " L1 im_ co.°,_,o..<br />
SPECIMEN_./ GAGE POINT / LVDT<br />
SURFACE (5/16" DIA. x 1/8")<br />
Figure<br />
3. Cross Section of LVDT Mounting<br />
136
Standard Method of Test for<br />
Determining Moisture Sensitivity Characteristics<br />
of Compacted Bituminous Mixtures Subjected<br />
to Hot and Cold Climate Conditions<br />
<strong>SHRP</strong> Designation: M-0061<br />
1. SCOPE<br />
1.1 This method determines the water sensitivity or stripping characteristics of<br />
compacted asphalt concrete mixtures under warm and cold climatic conditions.<br />
1.2 This standard may involve hazardous materials, operations, and equipment. This<br />
standard does not purport to address all of the safety problems associated with its use. It is<br />
the responsibility of the user of this standard to establish appropriate safety and health<br />
practices and determine the applicability of regulatory limitations prior to use.<br />
1.3 The values stated in SI units are to be regarded as the standard. The values in<br />
parentheses are for information only.<br />
2. REFERENCED DOCUMENTS<br />
2.1 AASHTO Documents<br />
MP1 Method of Test for Performance-Graded Asphalt Binder<br />
R 11 Practice for Indicating Which Places of Figures are to be Considered Significant in<br />
Specifying Limiting Values<br />
T2 Method for Sampling Aggregates<br />
T27 Method for Sieve Analysis of Fine and Coarse Aggregates<br />
T40 Method for Sampling Bituminous Materials<br />
T164 Method for Quantitative Extraction of Bitumen from Bituminous Paving Mixtures<br />
T167 Method for Compressive Strength of Bituminous Mixtures<br />
T168 Method of Sampling Bituminous Paving Mixtures<br />
T247 Method for Preparation of Test Specimens of a Bituminous Mixture by Means of<br />
the California Kneading Compactor<br />
T269 Method for Percent Air Voids in Compacted Dense and Open Bituminous Paving<br />
Mixtures<br />
1This standard is based on <strong>SHRP</strong> Product 1024.<br />
137
M-002 Preparation of Compacted Concrete Specimens of Modified and Unmodified Hot<br />
Mix Asphalt by Means of the <strong>SHRP</strong> Gyratory Compactor<br />
M-008 Preparation of Test Specimens of Bituminous Mixtures by Means of Rolling Wheel<br />
Compaction<br />
M-007 Short- and Long-Term Aging of Asphalt Concrete Mixtures<br />
2.2 ASTM Documents<br />
D 8 Standard Definitions of Terms Relating to Materials for Roads and Pavements<br />
D 3497 Standard Test Methods for Dynamic Modulus of Asphalt Mixtures<br />
D 3549 Method for Thickness or Height of Compacted Bituminous Paving Mixture<br />
Specimens<br />
E 1 Specification for Thermometers<br />
3. TERMINOLOGY<br />
3.1 Definitions for many terms to asphalt are found in the following documents:<br />
3.1.1 ASTM D8 Standard Definitions<br />
3.1.2 AASHTO MP1 Performance-Graded Asphalt Binder<br />
4. SUMMARY OF PRACTICE<br />
4.1 Compacted asphalt concrete test specimens are subjected to a water and<br />
temperature conditioning process. The water sensitivity characteristics of the compacted<br />
mixtures are determined based upon measurements of percent stripping, the environmental<br />
conditioning system (ECS) modulus, and the coefficients of permeability for air and water<br />
flow.<br />
5. SIGNIFICANCE AND USE<br />
5.1 The measured water sensitivity characteristics may be used to evaluate or<br />
characterize asphalt concrete mixtures.<br />
5.2 The water sensitivity characteristics of asphalt concrete mixtures can be used to<br />
determine their suitability for use as highway paving materials. This information may also be<br />
used to compare and select binders, modifiers, mixtures, additives, and aggregates for<br />
asphalt concrete.<br />
138
6. APPARATUS<br />
6.1 Environmental Condition System (ECS)--Any closed-loop computer-controlled<br />
test system that meets the minimum requirements outlined in table 1. The ECS must be<br />
capable of within an asphalt concrete specimen increasing the temperature to 100°C and<br />
decreasing it to -20°C within 2 hours. It must be able to "pull" distilled water through a<br />
specimen at specified vacuum levels. The ECS must be able to apply axial load pulses (220<br />
4- 5 N static and 6700 4- 25 N dynamic) in a haversine wave form with a load duration of<br />
0.1 s and a rest period of 0.9 s between load pulses. The system must also be capable of<br />
measuring axial deformations and be equipped with computer software which can compute<br />
axial compressive stress and recoverable axial deformation strain at various load cycles. In<br />
addition, the ECS must be capable of applying loads sufficient to obtain deformations<br />
between 50 to 100 #strain. The ECS is illustrated in figures 1, 2, and 3.<br />
Table 1. Minimum<br />
Test System Requirements<br />
Measurement and Control<br />
Parameters Range Resolution Accuracy<br />
Load (compression) 0 to 6700 N _< 2.5 N + 5 N<br />
Axial Deformation 0 to 6.5 mm < 0.0001 + 0.0001<br />
Chamber Temperature -20 to 100*C _< 0.5°C + 0.5oc<br />
Vacuum Pressure 0 to 635 mm Hg < 25 nun Hg + 25 mm Hg<br />
Air Flow 20 to 20,000 cm3/min < 20 cm3/min + 10 cm3/min<br />
Water Flow 0 to 2525 cm3/min < 2 cm3/min -1- 1 cm3/min<br />
Water Reserve Temperature 25 + 3°C < 0.50C + 0.5°C<br />
6.2 Testing Machine--a pneumatic or hydraulic testing machine that meets the<br />
requirements outlined in section 4.3 of T167.<br />
6.3 Specimen End Platens--Two aluminum end platens are shown in figure 4. The<br />
end platens shall be 102 4- 2 mm diameter by 51 4- 2 mm thick. Each end platen will have a<br />
drainage hole at its center that is 4.76 4- 0.5 mm in diameter and one side of each end platen<br />
will be patterned with grooves as shown in figure 4. In addition, the platen must have a<br />
groove around its perimeter at mid height which is of sufficient width and depth to hold the<br />
O-rings described in section 6.5.2.<br />
6.4 Perforated Teflon Disks--As shown in figure 4. The perforations must coincide<br />
with the grooving pattern in the specimen end platens.<br />
139
6.5 Miscellaneous Apparatus:<br />
6.5.1 150 mm of 100 mm diameter rubber membrane capable of covering the<br />
cylindrical surface area of the specimen.<br />
6.5.2 Two 102 mm O-rings<br />
6.5.3 Caulking gun<br />
6.5.4 Calipers<br />
6.5.5 Spatula<br />
6.5.6 Vacuum source<br />
7. MATERIALS<br />
7.1 The following materials are required:<br />
7.1.1 Clear silicone sealant (e.g., general household sealant, silicon rubber)<br />
7.1.2 Compressed air<br />
7.1.3 40 L of distilled water<br />
8. SAMPLING<br />
8.1 Asphalt binder shall be sampled in accordance with AASHTO T40.<br />
8.2 Aggregate shall be sampled in accordance with AASHTO T2.<br />
8.3 Asphalt concrete mixtures shall be sampled in accordance with AASHTO T168.<br />
9. SPECIMEN PREPARATION<br />
9.1 Prepare an asphalt concrete mixture sample in accordance with sections 9.1, 9.2,<br />
and 9.3 of T247. Prepare a sufficient amount of material to ensure that the final compacted<br />
test specimen is 102 + 4 mm in diameter by 102 + 4 mm in height.<br />
9.2 Subject the asphalt concrete mixture prepared in section 9.1 to short-term aging<br />
in accordance with sections 10.1, 10.2, and 10.3 of T247.<br />
"I"247.<br />
NOTE 1.--Plant mixed asphalt concrete samples are not to be subjected to short-term aging as described in<br />
140
9.3 Heat or cool the asphalt concrete mixture to the described compaction<br />
temperature.<br />
9.4 Compact the asphalt concrete mixture in accordance with T247. Compact a<br />
sufficient amount of material to ensure that the final compacted test specimen is 102 ___4 mm<br />
in height.<br />
9.5 Determine the air void of the specimen.<br />
NOTE2.--It is not recommended that the Marshall method of compaction (AASHTO T245-82 or ASTM<br />
D 1559-89) be used. If specimens are cored from the field or from a slab, the top and bottom of the specimen must<br />
not sustain a cut surface.<br />
9.6 Measure the diameter and height or thickness of the specimen at three locations,<br />
at approximately one-third points and record the average measurement as the diameter and<br />
thickness of the specimen + 1.0 mm in accordance with D 3549.<br />
9.7 Place the specimen inside the 150-mm long rubber membrane, centering the<br />
specimen within the membrane so that there is a 25-mm overlap at each end. Inject a<br />
continuous line of silicone cement between the membrane and the specimen with a caulking<br />
gun. Use a spatula to smooth the silicone to a thick, uniform layer between the rubber<br />
membrane and the specimen. Allow the specimen to stand at room temperature, overnight or<br />
longer, until the silicone is dry.<br />
10. PROCEDURE<br />
10.1 Specimen Setup<br />
10.1.1 Place a perforated Teflon disk on top of the grooved surface of the bottom<br />
end platen inside the load frame.<br />
10.1.2 Place the specimen vertically on top of the Teflon disk and bottom end platen.<br />
NoTE 3.--For cores removed from field pavements, it is important that the specimen be placed such that the<br />
top of the specimen corresponds to the top of the pavement.<br />
10.1.3 Place a perforated Teflon disk on top of the specimen and place the top end<br />
platen on top of the disk, with the grooved surface facing the disk and specimen.<br />
10.1.4 Seal the rubber membrane around the specimen platen assembly by placing an<br />
O-ring in each groove of the end platens, over the rubber membrane.<br />
10.1.5 To ensure that the system is airtight, select vacuum with the water-vacuum-air<br />
valve. This closes the system to air and water. Open the vacuum valve until the inlet and<br />
outlet pressure reads 510 mm of Hg. Adjust the vacuum level with the vacuum regulator.<br />
Close the vacuum valve. Close the bypass valve so that the vacuum is drawn through the<br />
141
specimen. Wait for 5 minutes. If both gauge readings remain constant, the system is airtight<br />
and testing may continue. If the readings decrease, the system is not airtight and adjustments<br />
must be made to the system prior to continuing testing.<br />
10.1.6 Attach the yoke with the spacers and the LVDTs to the specimen.<br />
10.2 Coefficient of Permeability for Air Flow<br />
10.2.1 Set and establish the temperature of the environmental control chamber to<br />
25 + 0.5°C.<br />
10.2.2 Open the vacuum valve and select air flow from the water-vacuum-air valve.<br />
Apply the lowest differential pressure possible (typically 50 mm of Hg) by adjusting the<br />
vacuum regulator. Record the air flow through the test specimen. Record the pressure<br />
differential reading.<br />
10.2.3 Repeat 10.2.2 for four different pressures. The pressures selected will vary<br />
depending on the void content of the specimen being tested. They may range from 50 to<br />
400 mm of Hg. It is important that a range be selected that is consistent with the air void<br />
content. A constant interval between the pressures must be selected e.g., 20, 30, 40, and<br />
50 kPa.<br />
10.2.4 Calculate the coefficient of permeability for air flow of the test specimen as<br />
described in 11.2.1 for each of the pressures. Report the average of the four results.<br />
NOTE4.--Air flow measurements should be within 10% of each other.<br />
10.2.5 Close the vacuum valve.<br />
10.3 ECS Modulus Test<br />
10.3.1 Maintain the temperature of the environmental chamber at 25 ___0.5°C.<br />
Remove the spacers from the yoke.<br />
10.3.2 Apply a static load of 130 + 25 N and an axial compressive repeated load of<br />
2200 + 25 N to the test specimen. The repeated load should be in a haversine wave form<br />
with a load duration of 0.1 s and a rest period of 0.9 s between load pulses.<br />
10.3.3 Adjust the specimen until the readings from the two LVDTs are within 15%<br />
of each other.<br />
10.3.4 If the strain is less than 50 _strain, increase the repeated load until a strain<br />
level between 50 and 100/_strain is reached. If the strain is more than 100/_strain, decrease<br />
the repeated load until a strain level between 50 and 100/_strain is reached.<br />
10.3.5 If using the ECS software, the load and deformation data for the last five<br />
cycles are collected and the ECS modulus automatically calculated when the [ESC] key is<br />
142
pressed. Otherwise, measure and record the peak axial load and recoverable vertical<br />
deformation for the load interval from the last five cycles. Then calculate the ECS modulus<br />
as outlined in section 11.3.3.<br />
NOTE 5.--Typically, to achieve a strain level of 100 + 5 #strain, a dynamic load approximately 4000 N is<br />
required. Once the load has been adjusted, use the same loads for subsequent measurements for the same specimen<br />
after the conditioning cycles.<br />
NoTE 6.--Do<br />
specimen.<br />
not exceed 250 load cycles when performing the ECS modulus test. This will damage the<br />
10.3.6 Remove the load from the specimen after the last load cycle. Check that the<br />
inlet and outlet gauges are closed.<br />
10.4 Vacuum<br />
valve.<br />
10.4.1 Check that the bypass valve is open. Select vacuum with the vacuum-water-air<br />
10.4.2 Open the vacuum valve and close the bypass valve. Apply a vacuum of<br />
510 mm of Hg for 10 min.<br />
10.4.3 Open the bypass valve.<br />
10.5 Wetting<br />
10.5.1 Maintain the temperature of the environment chamber at 25 + 0.5°C.<br />
Establish the temperature of the distilled water source at 25 + 3°C (room temperature).<br />
Open the bypass valve.<br />
10.5.2 Select water flow from the vacuum-water-air valve. Turn on the vacuum and<br />
adjust using the vacuum regulator until a level of 510 + 25 mm of Hg (as measured by the<br />
outlet gauge) has been reached.<br />
10.5.3 Wait for one minute or until distilled water has been drawn into the tubing<br />
and the system. Close the bypass valve so that the distilled water is pulled through the test<br />
specimen for 30 + 1 min.<br />
10.6 Coefficient of Permeability of Water Flow<br />
10.6.1 Decrease the vacuum level to approximately 40 kPa (5.8 psi) differential<br />
pressure by adjusting the vacuum regulator. Record the water flow through the test specimen.<br />
Record the pressure differential reading.<br />
10.6.2 Repeat the procedure described in section 10.6.1 for four different pressures.<br />
The pressures selected will vary depending on the void content of the specimen being tested.<br />
143
They may range from 20 to 40 kPa differential pressure.<br />
selected that is consistent with the air void content.<br />
It is important that a range be<br />
10.6.3 Calculate the coefficient of permeability for water flow as described in section<br />
11.5.1 for each pressure. Report the average result.<br />
NOTE7.--Water<br />
flow measurements should be within 10% of each other.<br />
10.7 Water Conditioning<br />
10.7.1 Conduct water conditioning for either the warm or cold climate conditions as<br />
described in sections 10.7.2 or 10.7.3, respectively. Table 2 summarizes the procedures<br />
described in sections 10.7.2 and 10.7.3.<br />
Table 2. Conditioning<br />
Cycles for Warm and Hot Climates<br />
Conditioning<br />
Stage<br />
Conditioning Factor Wetting* Cycle-1 Cycle-2 Cycle-3 Cycle-4<br />
Vacuum Level (ram Hg) 510 250 250 250 250<br />
Repeated Loading NO YES YES YES NO<br />
Ambient Temperature (°C)** 25 60 60 60 - 18<br />
Duration (hrs) 0.5 6 6 6 6<br />
Conditioning Procedure for Warm Climates<br />
Conditioning Procedure for Cold Climate<br />
*Wetting the specimen prior to the conditioning cycles<br />
**inside the environmental cabinet<br />
Notes:<br />
1. The conditioning procedure for a warm climate is wet, then 3 hot cycles.<br />
2. The conditioning procedure for a cold climate is wet, then 3 hot cycles plus one cold cycle.<br />
10.7.2 Warm Climate Conditioning<br />
10.7.2.1 Reduce the vacuum pressure to 254 -I- 25 mm Hg at the outlet gauge and<br />
reduce the water flow to 4 + 1 cm3/min.<br />
10.7.2.2 Set the temperature of the environmental cabinet to 60 + 0.5°C for 6 hours<br />
+ 5 min, followed by a temperature of 25 + 0.5°C for at least 2 hours.<br />
144
10.7.2.3 Apply a repeated axial compressive load of 90 + 5 N static and 900 +<br />
25 N dynamic to the test specimen, in a haversine wave form with a load duration of 0.1 s<br />
and a rest period of 0.9 s between load pulses. Continuous application of the load is to occur<br />
throughout the hot conditioning cycle (i.e., 6 hours at 60°C).<br />
NOTE 8.--For<br />
open-graded mixes, the loads may need to be reduced.<br />
10.7.2.4 At the end of 8 hours, close the vacuum valve, open the bypass valve and<br />
open the system to atmospheric pressure. Continue to maintain the temperature setting of the<br />
environmental chamber at 25 + 0.5°C. Determine the ECS modulus as described in section<br />
10.3.<br />
NOTE 9.--For the modulus test, use the same loads that were initially established in section 10.3.<br />
10.7.2.5 Continue to maintain temperature setting of the environmental chamber at<br />
25 + 0.5°C and determine the coefficient of permeability of water flow as described in<br />
section 10.6.<br />
NOTE 10.--If excessive deformation (5 to 10%) of the specimen is experienced after the first hot cycle,<br />
terminate the conditioning.<br />
10.7.2.6 Begin a second hot conditioning cycle by repeating the procedure in sections<br />
10.7.2.1 to 10.7.2.5.<br />
10.7.2.7 Begin a third hot conditioning cycle by repeating the procedure in sections<br />
10.7.2.1 to 10.7.2.5.<br />
10.7.3 Cold Climate Conditioning<br />
10.7.3.1 Complete the three hot conditioning cycles as described in sections 10.7.1.<br />
to 10.7.2.7.<br />
10.7.3.2 Reduce the vacuum pressure to 250 + 25 mm Hg at the outlet gauge and<br />
reduce the water flow to 4 + 1 cm3/min. Turn off the load.<br />
10.7.3.3 Set the temperature of the environmental chamber to -18 + 0.5°C for<br />
6 hours + 5 min followed by a temperature of 25 + 0.5°C for at least 2 hours.<br />
10.7.3.4 At the end of the 8 hours, close the vacuum valve, open the bypass valve<br />
and open the system to atmospheric pressure. Continue to maintain the temperature setting of<br />
the environmental chamber at 25 + 0.5°C. Determine the ECS resilient modulus as<br />
described in section 10.3.<br />
10.7.3.5 Continue to maintain the temperature setting of the environmental chamber<br />
at 25 + 0.5°C and determine the coefficient of permeability of water flow as described in<br />
section 10.6.<br />
145
10.8 Stripping Evaluation<br />
10.8.1 At the conclusion of the last conditioning cycle, remove the specimen from<br />
the environmental chamber. Remove the membrane from the specimen and place it in a<br />
diametral position between two bearing plates of a loading jack on a mechanical or hydraulic<br />
testing machine.<br />
10.8.2 Apply a load sufficient to induce a vertical crack in the specimen.<br />
10.8.3 Remove the test specimen and pull the two halves apart. Estimate the<br />
percentage of stripping that has occurred by making a relative comparison to the standard<br />
patterns of stripping shown in figure 6.<br />
11. CALCULATIONS<br />
11.1 Calculate the following:<br />
11.1.1 Cross Sectional Area (m2):<br />
A---<br />
_rd 2<br />
40,000 (1)<br />
where<br />
d = Average diameter of the test specimen, in cm<br />
_r = 3.14159<br />
11.2 After conducting the air permeability testing outlined in section 10.2, calculate<br />
the following:<br />
11.2.1 Coefficient of Permeability of Air Flow (cm/s):<br />
where<br />
ka = 1.7937 × 10-8qL<br />
AP (2)<br />
ka = Coefficient of permeability for air flow, in cm/s<br />
q = Flow rate of air at mean pressure across specimen, in cm3/min<br />
L = Average height of the test specimen, in mm<br />
AP = Pressure difference across the specimen, mm Hg<br />
11.3 For the last five load cycles applied as specified in section section 10.3,<br />
calculate the following:<br />
NOTE 11.--The ECS software should automatically make the computations described in sections 11.3, 11.4,<br />
and 11.6.1.<br />
146
11.3.1 Peak Stress (kPa) per load cycle:<br />
where<br />
V__n = Peak load applied by the vertical actuator over a load cycle, in N<br />
i --- Number of conditioning cycles applied (i.e., 0, 1...4)<br />
n = Number of load cycles applied (i.e., 1, 2, 3, 4, 5)<br />
11.3.2 Recoverable Axial Strain (mm/mm) per load cycle:<br />
_ri-n<br />
_'i-n =<br />
2h (4)<br />
where<br />
_ri-n = Peak recoverable vertical deformation over a load cycle, in mm<br />
h = Gauge length, the distance over which deformations are measured (i.e,<br />
distance between yoke rings), in mm<br />
NOTE 12.--The recoverable deformation is the position of the total deformation that disappears (or is<br />
recovered) upon unloading the specimen as shown in figure 7.<br />
11.3.3 ECS Modulus (kPa) per load cycle:<br />
MR,_" : cri-n1 (5)<br />
11.4 After calculating ECS modulus for the last five load cycles, calculate the<br />
following:<br />
where<br />
11.4.1 Average ECS Modulus (kPa) per conditioning cycle:<br />
5<br />
E (u,,_n)<br />
Mm - n=l<br />
An (6)<br />
An = the number of load cycle included in M_ calculation (for last five load<br />
cycles, An = 5)<br />
147
11.5 After conducting the water permeability testing outlined in section 10.6,<br />
calculate the following:<br />
where<br />
11.5.1 Coefficient of Permeability for Water Flow (cm/s):<br />
kw = 7.4075 × 10-6qL<br />
AP (7)<br />
kw = Coefficient of permeability for water flow, in cm/s<br />
q = Flow rate of water at mean pressure across specimen, in cm3/min<br />
L = Average height of the test specimen, in mm<br />
AP = Pressure difference across the specimen, in kPa<br />
11.6 After completing each conditioning cycle (i), compute the following:<br />
11.6.1 ECS Modulus Ratio."<br />
where<br />
MRo = Initial ECS resilient modulus, in kPa<br />
11._2 Water Permeability Ratio:<br />
(8)<br />
where<br />
tk o/<br />
K,_ = Initial water permeability, in cm/s<br />
12. REPORT<br />
12.1 Report the following information:<br />
12.1.1 Asphalt Binder Grade<br />
12.1.2 Asphalt Binder Content--in percent to the nearest 0.1%<br />
148
12.1.3 Aggregate Type and Gradation<br />
12.1.4 Mixing and Compaction Conditions--the following information is applicable:<br />
12.1.4.1 Plant Mixing Temperature--in degrees Celsius to the nearest I°C<br />
12.1.4.2 Laboratory Mixing Temperature--in degrees Celsius to the nearest 1 °C<br />
12.1.4.3 Laboratory Compaction Temperature--in degrees Celsius to the nearest 1°C<br />
12.1.4.4 Laboratory Compaction Method<br />
12.1.4.5 Compacted Specimen Height--in centimeters to the nearest 0.15 cm<br />
12.1.4.6 Compacted Specimen Diameter--in centimeters to the nearest 0.15 cm<br />
12.1.4.7 Compacted Specimen Area--in square centimeters to the nearest 0.02 cm /<br />
12.1.4.8 Compacted Specimen Density--in kilograms per square meter to the nearest<br />
0.02 cm 2<br />
12.1.4.9 Compacted Specimen Air Voids--in percent to the nearest 0.1%<br />
12.1.5 Coefficient of Permeability for Air Flow--a table listing of the following<br />
results for each different pressure applied:<br />
12.1.5.1 Chamber Testing Temperature--in degrees Celsius to the nearest 0.5°C<br />
12.1.5.2 Differential Pressure--in mm of Hg<br />
12.1.5.3 Air Flow--in cubic centimeters per second to the nearest 2 cm3/s<br />
12.1.5.4 Coefficient of Permeability for Air Flow--in cm/s to the nearest 2 cm/s<br />
12.1.6 ECS Modulus Results--a table listing the following results for each load cycle<br />
(last five cycles) prior to any conditioning cycles and after each conditioning cycle:<br />
12.1.6.1 Chamber of Testing Temperature--in degrees Celsius to the nearest 0.5°C<br />
12.1.6.2 Static Load Applied--in newtons to the nearest 5 N<br />
12.1.6.3 Dynamic Load Applied--in newtons to the nearest 5 N<br />
12.1.6.4 Peak Stress--in kilopascals to the nearest 0.1 kPa<br />
149
12.1.6.5 Recoverable Axial Strain--in millimeters per millimeter to the nearest 10 -6<br />
mm/rnm<br />
12.1.6.6 ECS Modulus--in kilopascals to the nearest 5 kPa<br />
12.1.7 Initial ECS Modulus--in kilopascals to the nearest 5 kPa<br />
12.1.8 Coefficient of Permeability for Water FIow--a table listing the following<br />
results for each differential pressure applied after each conditioning cycle:<br />
12.1.8.1 Chamber Testing Temperature--in degrees Celsius to the nearest 0.5°C<br />
12.1.8.2 Water Temperature--in degrees Celsius to the nearest 0.5°C<br />
12.1.8.3 Differential Pressure--in kpa to the nearest 5 kpa<br />
12.1.8.4 Water Flow--in cubic centimeters per minute to the nearest 2 cm3/min<br />
nearest<br />
12.1.8.5 Coefficient of Permeability of Water Flow--in centimeters per second to the<br />
10-4 cm/s<br />
12.1.9 Water Conditioning Results--a table listing the following results for each<br />
conditioning cycle:<br />
12.1.9.1 Average ECS Modulus--in kPa to the nearest 5 kPa<br />
12.1.9.2 ECS Modulus Ratio<br />
12.1.9.3 Water Permeability Ratio<br />
12.1.10 Stripping Rate--in percent to the nearest 5 %<br />
13. PRECISION<br />
13.1 Data to support a precision statement for this test method are not available.<br />
13.2 Since there is no accepted reference value, the bias for this test method cannot<br />
be determined.<br />
14. KEYWORDS<br />
14.1 Asphalt concrete, asphalt concrete permeability, bituminous mixtures,<br />
bituminous paving mixtures, moisture sensitivity, resilient modulus, stripping potential, water<br />
sensitivity.<br />
150
Specimen Temperature Hi/Lo Limit Programmable Temperature<br />
Readout Controller /Controller<br />
Function<br />
Switches<br />
I<br />
0 0<br />
m<br />
| I<br />
i /<br />
I<br />
•<br />
Water<br />
Conditioning<br />
Control Panel<br />
(on hinged<br />
Load Frame<br />
Environmental Chamber<br />
mounting)<br />
mmmmmmmmmm<br />
mmmmmmmmmmmmm<br />
mmmmmmmmmmmmmmm<br />
mmmmmmmmmmmmmm<br />
m mmmmmmmmm mm_mm m m m<br />
mmmmmmmmmmmmmmm<br />
mmmmmmmmmmmm<br />
mmmmmmmmmmmmmm<br />
mmmmmmmmmmmmmmmm<br />
Figure I. Environmental Conditioning System (Front View)<br />
151
Tie Rods (4)<br />
Servovalve<br />
Air Cylinder<br />
Exhaust Muffler _ Compressed<br />
Air Supply<br />
Top Plate Load Cell<br />
LVDT<br />
LVDT<br />
Top Platen _Teflon Spacer<br />
Specimen _ Specimen Clamps<br />
Teflon Spacer _ Bottom Platen<br />
Base Plate<br />
Figure 2. Load Frame with Specimen<br />
152
i<br />
Pressure Differential Gauge<br />
/_ 0 0 _l 0 0<br />
I<br />
Specimen Inlet<br />
Gauge<br />
I<br />
i-Q<br />
:imen Outlet<br />
Gauge<br />
Valve; Gauge 1, ; Gauge 2,<br />
Vent/Off o vlmjmlll vent/off<br />
Valve;<br />
I11-_ o Flowmeters, Air<br />
Air-Water-Vacuum<br />
Mode Selector<br />
-- -<br />
ItSELf, __Valve;<br />
On-Off<br />
Air,<br />
Valve; Vacuum _.L = _Valve; Water,<br />
VacuumOn-Off Regulator --_°':U _ __.___ 1ol _1_ o!1o1_ _. ° Flowmeters, Water On-Off<br />
Figure 3. Control Panel<br />
153
Drainage<br />
Hole<br />
3/16" wide X 3/32" deep grooves<br />
Figure 4. Groove Pattern for End Platens<br />
154
I0 0 0 0 0 0 0<br />
0 0 Ooo00 0 0<br />
'_,Oo O O O -oO/<br />
Figure 5. Perforated<br />
Teflon Spacers<br />
155
Specimen to be<br />
evaluated goes here<br />
5% 10%<br />
or here<br />
20% 30%<br />
or here<br />
40% 50%<br />
Figure 6. Stripping Rate Standards<br />
156
" Total Elastic<br />
0<br />
Ei._<br />
0<br />
121<br />
Plastic<br />
Deformation<br />
Time<br />
Figure 7. Illustration of Specimen Deformation Resulting<br />
from Application of Load Cycles<br />
157
Standard Method of Test for<br />
Short-<br />
and Long-Term Aging of Bituminous Mixes<br />
<strong>SHRP</strong> Designation: M-0071<br />
1. SCOPE<br />
1.1 This method describes the short- and long-term aging procedures for compacted<br />
and uncompacted bituminous mixtures. Two types of aging are described: 1) short-term aging<br />
of uncompacted mixtures to simulate the precompaction phase of the construction phase, and<br />
2) long-term aging of compacted mixtures to simulate the aging that occurs over the service<br />
life of a pavement. The long-term aging procedures should be preceded by the short-term<br />
aging procedure. Evaluation of the extent of aging should be performed using a resilient<br />
modulus test (ASTM D 4123-82), dynamic modulus test (ASTM D 3497-79) or other<br />
approved test.<br />
1.2 This standard may involve hazardous materials, operations and equipment. This<br />
standard does not purport to address all of the safety problems associated with its use. It is<br />
the responsibility of the user of this standard to establish appropriate safety and health<br />
practices and determine the applicability of regulatory limitations prior to use.<br />
1.3 The values stated in SI units are to be regarded as the standard. The values in<br />
parentheses are for information only.<br />
2. REFERENCED DOCUMENTS<br />
2.1 AASHTO Documents:<br />
MP1 Test Method for Performance-Graded Asphalt Binder<br />
R 11 Practice for Indicating Which Places of Figures are to be Considered Significant in<br />
Specifying Limiting Values<br />
T2 Methods of Sampling Stone, Slag, Gravel, Sand, and Stone Block for Use as<br />
Highway Materials<br />
T27<br />
T40<br />
Method for Sieve Analysis of Fine and Coarse Aggregates<br />
Method of Sampling Bituminous Materials<br />
T164 Methods of Test for Quantitative Extraction of Bitumen fromn Bituminous Paving<br />
Material<br />
T168 Methods of Sampling Bituminous Paving Mixtures<br />
_Thisstandardis basedon <strong>SHRP</strong>Products1025and1030.<br />
159
T201 Method of Test for Kinematic Viscosity of Asphalts<br />
T269 Method for Percent Air Voids in Compacted Dense and Open Bituminous Paving<br />
Mixtures<br />
M-002 Preparation of Compacted Specimens of Modified and Unmodified Hot Mix Asphalt<br />
by Means of the <strong>SHRP</strong> Gyratory Compactor<br />
M-008 Preparation of Test Specimens of Bituminous Mixtures by Means of Roiling Wheel<br />
Compaction<br />
2.2 ASTM Documents:<br />
D 8 Standard Definitions of Terms Relating to Materials for Roads and Pavements<br />
D 3497 Standard Test Methods for Dynamic Modulus of Asphalt Mixtures<br />
D 3549 Method for Thickness or Height of Compacted Bituminous Paving Mixture<br />
Specimens<br />
D 4123 Method for Indirect Tension Test for Resilient Modulus of Bituminous Mixes<br />
E 1 Specification for Thermometers<br />
3. TERMINOLOGY<br />
3.1 Desired Mixing Temperature--the target temperature for mixing asphalt binder<br />
and aggregate in the laboratory. The desired mixing selected should be equivalent to the<br />
anticipated field plant mixing temperature. If field mixing temperatures are unknown, select a<br />
temperature which corresponds to a kinematic viscosity of 170 + 20 mm2/s for the asphalt<br />
binder.<br />
3.2 Desired Mixing Temperature--the target temperature for mixing asphalt binder<br />
and aggregate in the laboratory. The desired mixing temperature should be equivalent to the<br />
anticipated field plant mixing temperature. If field mixing temperatures are unknown, select a<br />
temperature which corresponds to a kinematic viscosity of 170 + 20 mm2/s for the asphalt<br />
binder which is used.<br />
3.3 Definitions for many terms common to asphalt are found in the following<br />
documents:<br />
3.3.1 ASTM D 8 Standard Def'mitions<br />
3.3.2 AASHTO MP1 Performance-Graded Asphalt Binder<br />
3.3.3 AASHTO T201 Kinematic Viscosity of Asphalts<br />
4. SUMMARY OF PRACTICE<br />
4.1 For short-term aging, a mixture of aggregate and asphalt binder is aged in a<br />
forced draft oven for 4 hours at 135°C. The oven aging is designed to simulate the aging the<br />
mixture would undergo during plant mixing and construction.<br />
160
4.2 For long-term aging, a compacted mixture of aggregate and asphalt binder is<br />
aged in a forced draft oven for 5 days at 85 °C. The oven aging is designed to simulate the<br />
total aging that the compacted mixture will undergo during 7 to 10 years of service.<br />
5. SIGNIFICANCE AND USE<br />
5.1 The short-term aging practice simulates the aging that asphalt concrete mixtures<br />
undergo during field plant mixing operations. The long-term aging practice simulates the inservice<br />
aging of asphalt concrete mixtures after field placement and compaction.<br />
5.2 The properties and performance of asphalt concrete mixtures may be more<br />
accurately predicted by using aged test samples.<br />
6. APPARATUS<br />
6.1 Aging Test System--A system that consists of a forced draft oven which possesses<br />
the requirements specified in table 1.<br />
Table 1. Minimum Aging Test System Requirements<br />
Range (°C) Resolution (°C) Accuracy (°C)<br />
Temperature 10-260 < 1 5=1<br />
Measurement<br />
Temperature Control 25-250 < 0.1 5=0.1<br />
6.2 Oven--Any oven which is thermostatically controlled and capable of being set to<br />
maintain any desired temperature from room temperature to 160°C. The oven shall be used<br />
for heating aggregates, asphalt binders, or laboratory equipment.<br />
6.3 Mixing Apparatus--Any type of mechanical mixer that: 1) can be maintained at<br />
the required mixing temperatures; 2) will provide a well-coated, homogenous mixture of the<br />
required amount of asphalt concrete in the allowable time; and 3) allows essentially all of the<br />
mixture to be recovered.<br />
6.4 Miscellaneous Apparatus<br />
6.4.1 One metal oven pan for heating aggregates<br />
6.4.2 One shallow metal oven pan for heating uncompacted asphalt concrete mixtures<br />
6.4.3 Thermometers that have a range of 50 to 260°C and conform to the<br />
requirements prescribed in ASTM Document E 1<br />
161
6.4.4 One metal spatula or spoon<br />
6.4.5 Oven gloves<br />
7. HAZARDS<br />
7.1 This test method involves the handling of hot asphalt binder, aggregate, and<br />
asphalt concrete mixtures. These materials can cause severe burns if allowed to contact skin.<br />
Proper precautions must be taken to avoid burns.<br />
8. SAMPLING<br />
8.1 The asphalt binder shall be sampled in accordance with T40.<br />
8.2 The aggregate shall be sampled and tested in accordance with T2 and T27,<br />
respectively.<br />
9. SPECIMEN PREPARATION<br />
9.1 Preheat the aggregate for a minimum of 2 h at the desired mixing temperature.<br />
The amount of aggregate preheated shall be of sufficient size to obtain a mixture specimen of<br />
the desired size.<br />
9.2 Preheat the asphalt binder to the desired mixing temperature. The amount of<br />
asphalt binder preheated shall be of sufficient size to obtain the desired asphalt binder content<br />
to be tested.<br />
NOTE 1.--Asphalt binders held for more than 2 h at the desired mixing temperature should be discarded.<br />
9.3 Mix the heated aggregate and asphalt binder at the desired asphalt content.<br />
10. PROCEDURE<br />
10.1 Place the mixture on the baking pan and spread it to an even thickness of<br />
approximately 21 to 22 kg/m 2. Place the mixture and pan in the forced draft oven for<br />
4 h + 5 min at a temperature of 135°C + 1°C.<br />
10.2 Stir the mixture every hour to maintain uniform aging.<br />
10.3 After 4 h, remove the mixture from the forced draft oven. The aged mixture is<br />
now ready for further conditioning or testing as required. Proceed to section 11 if the<br />
specimens are not conditioned for the effects of long-term aging.<br />
162
10.4 Sampling<br />
T164.<br />
10.4.1 Plant-mixed asphalt concrete mixtures shall be sampled in accordance with<br />
10.4.2 Laboratory-mixed asphalt concrete mixtures shall be sampled, prepared and<br />
aged in accordance with T164.<br />
10.4.3 Compacted roadway samples shall have a cut test specimen size that is<br />
102 5:6 mm in diameter by 152 5:6 mm in height.<br />
10.5 Heat the asphalt concrete to the desired compaction temperature.<br />
10.6 Compact the sample in accordance with M-002 or M-008.<br />
NOTE2.--Compacta sufficientamountof materialto ensurethat thefinaltestspecimensizeis<br />
102+ 6 mmin diameterby 152 4-6 mmin height.<br />
10.7 Cool the compacted test specimen to 60°C 5: 1°C in an oven set at 60°C.<br />
NOTE3.--Coolingto 60°Cwilltakeapproximately2 h forthe testspecimensizestatedin note2.<br />
10.8 After cooling the test specimen to 60°C, level the specimen ends by applying a<br />
static load to the specimen at a rate of 72.00 + .05 kN/min. Release the load at the same<br />
rate when the specimen ends are level or when the load applied reaches a maximum of<br />
56 kN.<br />
10.9 After cooling the test specimen at room temperature overnight, extrude the<br />
specimen from the compaction mold.<br />
10.10 Place the compacted test specimen on a rack in the forced draft oven for<br />
120 5:0.5 h at a temperature of 85°C 5: I°C.<br />
10.11 After 120 h, turn the oven off, open the doors, and allow the test specimen to<br />
cool to room temperature. Do not touch or remove the specimen until it has cooled to room<br />
temperature.<br />
NoTE4.--Coolingto roomtemperaturewilltakeapproximatelyovernight for the testspecimensizestated<br />
in note21.<br />
10.12 After cooling to room temperature, remove the test specimen from the oven.<br />
The aged specimen is now ready for testing as required.<br />
11. REPORT<br />
11.1 Report the following information:<br />
163
11.1.1 Asphalt Binder Grade<br />
11.1.2 Asphalt Binder Content--in percent to the nearest O.1%<br />
11.1,3 Aggregate Type and Gradation<br />
11.1.4 Short-Term Aging Conditions--the following information as applicable:<br />
11.1.4.1 Plant-Mixing Temperature--in degrees Celsius to the nearest 1°C<br />
11,1.4.2 Laboratory-Mixing Temperature--in degrees Celsius to the nearest I°C<br />
11.1.4.3 Short-Term Aging Temperature in Laboratory--in degrees Celsius to the<br />
nearest 1°C<br />
11.1.4.4 Short-Term Aging Duration in Laboratory--in minutes to the nearest 1 min<br />
11.1.5 Long-Term Aging Conditions<br />
11.1.5.1 Compaction Temperature--in degrees Celsius to the nearest 1 °C<br />
11.1.5.2 Compacted Specimen Height--in millimeters to the nearest 1 mm<br />
11.1.5.3 Compacted Specimen Diameter--in millimeters to the nearest 1 mm<br />
11.1.5.4 Compacted Specimen Density--in kilograms per square meter to the nearest<br />
1 kg/m2<br />
11.1,5.5 Compacted Specimen Air Voids--in percent to the nearest O.1%<br />
11.1.5.6 Long-Term Aging Temperature--in degrees Celsius to the nearest 1°C<br />
11.1.5.7 Long-Term Aging Duration--in minutes to the nearest 1 rain<br />
12. KEY WORDS<br />
12.1 Aging, asphalt concrete, asphalt concrete aging, bituminous mixtures,<br />
bituminous paving mixtures, short-term aging.<br />
164
Standard<br />
Practice for<br />
Preparation of Test Specimens of Bituminous Mixtures<br />
by Means of Rolling Wheel Compaction<br />
<strong>SHRP</strong> Designation: M-0081<br />
1. SCOPE<br />
1.1 This method describes the mixing and compactionprocedures to produce large<br />
slab specimens (approximately101.6 mm × 762 mm× 762 ram) of bituminous concrete in<br />
the laboratory by meansof a mechanicalrolling wheel compactor.It also describes the<br />
procedure for determiningthe air void content of the specimens obtained.<br />
1.2 The values stated in SI units are to be regarded as the standard.<br />
1.3 This standard may involve hazardous materials, operations and equipment. This<br />
standard does not purport to address all of the safety problems associated with its use. It is<br />
the responsibility of the user of this standard to establish appropriate safety and health<br />
practices and determine the applicability of regulatory limitations prior to use.<br />
2. APPLICABLE DOCUMENTS<br />
2.1 AASHTO Test Methods:<br />
T11-85 Amountof Material Finer than 75-#rn Sieve in Aggregate<br />
T27-84 Sieve Analysis of Fine and Coarse Aggregates<br />
T246-81 Resistanceto Deformation and Cohesion of BituminousMixturesby Means of<br />
Hveem Apparatus<br />
2.2 ASTM Test Methods:<br />
C 117-90<br />
C 136-84a<br />
MaterialsFiner than 75-#m (No. 200) Sieve in Mineral Aggregates by<br />
Washing<br />
Sieve Analysis of Fine and Coarse Aggregates<br />
ZThis standard is based on <strong>SHRP</strong> Product 1015.<br />
165
D 1561-81a Preparation of Bituminous Mix Test Specimens by Means of California<br />
Kneading Compactor<br />
D 2041-78 Test Method for Theoretical Maximum Specific Gravity of Bituminous Paving<br />
Mixtures<br />
D 2493-91 Standard Viscosity Temperature Chart for Asphalts<br />
3. APPARATUS<br />
3.1 Rolling Wheel Compactor--A mechanical, self-propelled rolling wheel compactor<br />
with forward/reverse control such as that shown in figure 1 for compaction of asphalt<br />
concrete mixtures. It must weigh a minimum of 1,000 kg and possess the capability of<br />
increasing the weight to 1,500 kg. The load applied must be in the static mode.<br />
3.2 Mold--A mold to hold the bituminous mix as shown in figure 2. The mold is<br />
composed of one lift 101.6 mm thick.<br />
3.3 Ovens--Forced-draft electric ovens of sufficient size, capable of maintaining a<br />
uniform temperature between 100 + 3°C and 200 4- 3°C. It is preferable to have ovens with<br />
a capacity of 2.8 x 10-2 m3 to 4.2 × 10-2 m 3 for asphalts and 0.7 m 3 to 0.85 m 3 for<br />
aggregates.<br />
3.4 Specimen Mixing Apparatus--Suitable mechanized mixing equipment is required<br />
for mixing the aggregate and the bituminous material. It must be capable of maintaining the<br />
bituminous mixture at the selected mixing temperature, and allow the aggregate to be<br />
uniformly and completely coated with asphalt during the mixing period (approximately<br />
4 min). It is preferable to have a mixer with a capacity of 7 x 10-2 m 3 to 8.5 × 10-2 m3. A<br />
conventional concrete mixer fitted with infrared propane heaters has been found to be<br />
suitable.<br />
3.5 Coring and Saw Cutting Equipment--Mechanized coring and saw cutting<br />
equipment capable of coring specimens 101.6 mm to 203.2 mm in diameter and beams of<br />
different sizes from an asphalt concrete slab. It is preferable to dry-cut the cores and beams.<br />
3.6 Balance--Two balances are required: one with a capacity of 5 kg or more and<br />
sensitive to 1.0 g or less, and the other with a capacity between 45 and 120 kg, and sensitive<br />
to 0.5 kg or less.<br />
166<br />
3.7 Miscellaneous Apparatus:<br />
3.7.1 Digital thermometers with thermocouple probe<br />
3.7.2 Spatulas, trowels, scoops, spades, rakes<br />
3.7.3 Heat-resistant gloves
3.7.4 Metal pans<br />
3.7.5 Socket wrench, sockets, screw drivers, crescent wrench<br />
3.7.6 Lubricant for mold (e.g., PAM ®cooking oil or equivalent)<br />
3.7.7 Tape measure<br />
3.7.8 Parafilm (manufactured by American National Can Co., Greenwich, CT)<br />
3.7.9 Pallet jack<br />
4. MATERIAL PREPARATION<br />
4.1 Aggregate--Aggregate to be used for specimen preparation should be prepared in<br />
accordance with AASHTO Tll-85 and T27-84. After the aggregate has dried to a constant<br />
weight, remove the aggregate from the oven, and cool to room temperature. Then sieve into<br />
the separate size fractions necessary to accurately recombine into test mixtures that conform<br />
to specified grading requirements.<br />
4.2 Determine material quantities--Calculate the quantity of material required to<br />
achieve the desired air void content. These calculations are shown in section 7.<br />
4.3 Mixing Temperature--Set the oven to the mixing temperature. For mixes<br />
employing unmodified asphalt cements, the temperature of the aggregate and the asphalt at<br />
the time mixing begins shall be in accordance with the temperatures specified in AASHTO<br />
T246-82 or ASTM D 1561-81a. The temperature selected should correspond to a viscosity of<br />
170 ± 20 mmE/s (based on the original asphalt properties).<br />
4.4 Heating the asphalt--Asphalts supplied in 19-L epoxy-coated containers must<br />
first be heated to 135°C in a forced draft oven. The container should be loosely covered with<br />
a metal lid. This first heating is to subdivide the 19-L sample into smaller containers for<br />
subsequent use. After approximately 1.5 h, remove the sample from the oven, and stir with a<br />
large spatula or metal rod. The sample should be stirred every half hour to ensure uniform<br />
heating. Typically, a 19-L sample will require approximately 5 h for the entire heating cycle.<br />
NOTE 1.--Watch for signs of blue smoke from the asphalt. This would indicate overheating. If a noticeable<br />
quantity of smoke is observed, then the oven temperature should be reduced by 5 to 10°C.<br />
Place paper or newsprint on the floor in a well-ventilated area. Place empty and clean<br />
1-L containers on the paper in a sequence convenient for pouring the hot asphalt. Differentsized<br />
containers may also be used. It is important that the containers be properly labelled<br />
with self-adhesive labels or a diamond-tipped pencil prior to pouring.<br />
Remove the 19-L container from the oven and stir the asphalt for approximately<br />
1 minute. Fill the containers, taking care that the labels on the containers are not obliterated.<br />
167
After filling, close all containers tightly, and allow to cool to room temperature. Store at a<br />
temperature of 10°C. Closing the containers prior to cooling will produce a vacuum seal.<br />
4.5 Prior to mixing, set the oven to the mixing temperature as determined in<br />
section 4.3. Place a sufficient number of 1-L cans (with a total weight greater than that<br />
calculated in section 7.8) of asphalt in the oven at least 2 h prior to mixing. Monitor the<br />
temperature of the asphalt periodically. When the temperature approaches the mixing<br />
temperature, transfer the asphalt into a large pot (e.g., an 11-L stock pot) and at the same<br />
time weigh the amount of asphalt added to the pot. Transfer enough asphalt to equal the<br />
amount calculated in section 7.8 plus an extra 80 g (to account for the quantity retained in<br />
the pot after asphalt has been added to the aggregate). Then place the pot in the oven and<br />
continue to monitor the temperature periodically.<br />
NOTE2.--This<br />
twice must be discarded.<br />
constitutes the second heating of the asphalt. Any asphalts that have been heated more than<br />
4.6 Mixing--Preheat the mixer approximately 1 h prior to mixing. Place coarse<br />
aggregate in the mixer, followed by the fine aggregate, and then the asphalt. Mix for<br />
approximately 4 min to ensure uniform coating of the aggregate.<br />
4.7 Short Term Aging--After mixing, remove the mixture from the mixer and place<br />
it in metal pans. Place the mixture in an oven set at a temperature of 135 ° + I°C for<br />
4 h + 1 min. Stir the mixture once an hour.<br />
5. COMPACTION<br />
5.1 Assemble the mold as shown in the schematic illustrated in figure 2. Preheat the<br />
mold with a "tent" equipped with infrared heat lamps (see figure 3).<br />
5.2 Check the oil and fuel levels in the rolling wheel compactor and refill if<br />
necessary. Start the compactor and allow it to warm up. Spray a mild soapy solution on the<br />
rollers.<br />
mold.<br />
5.3 Sparingly apply a light oil (e.g., PAM ® cooking oil) to the base and sides of the<br />
5.4 Remove a pan of mixture from the oven and place it in the center of the mold.<br />
Level the mixture using a rake while at the same time avoiding any segregation of the<br />
mixture (i.e., avoid any tumbling of the coarse aggregate). Repeat this process until the mold<br />
is filled with the required quantity of material to achieve the target air void content. This<br />
should be all of the pre-weighed material. Tamp the mixture to achieve as level a surface as<br />
possible.<br />
5.5 Monitor the temperature of the mixture at the surface, at mid-depth, and at the<br />
bottom in various locations. Allow the mixture to cool until the coolest temperature<br />
corresponds to the pre-established compaction temperature (see notes 3 and 4).<br />
168
NOTE3.--The field compaction temperature should be used. As general guide, the compaction temperature<br />
to be used for most typical asphalt cements (AC-5 to AC-30) should correspond to an equiviscous temperature of<br />
280 + 30 mm2/s (based on original binder properties) as described in section 4.3. If necessary, the mixture should<br />
be placed in an oven until it reaches a uniform temperature.<br />
NoTE 4.--Lower compaction temperatures in the range between 115°C and 138°C may be necessary<br />
depending on the compactibility of the mixtures used under the rolling wheel compactor.<br />
5.6 Compact the mature until the rollers bear down on the compaction stops (steel<br />
channels with depths equal to slab thickness inserted in the mold as shown in figure 2).<br />
When compacting, each pass of the roller must extend from the ramp to the platform in a<br />
continuous motion, with no stops on the mixture. After the first few passes, it may be<br />
necessary to scrape bituminous mixture off the rollers and reshape the mixture.<br />
5.7 When compaction is complete, let the slab cool overnight (typically 15 to 16 h)<br />
before removing the mold. If the slab is still warm to the touch, do not remove the mold. Do<br />
not place any weights on top of the slab.<br />
5.8 After the slab is completely cooled, remove the slab from the mold together with<br />
the removable base of the mold (constructed of particle board) before placing on a pallet<br />
jack.<br />
5.9 The slab should be dry cored and sawn into the desired specimen shapes as soon<br />
as possible. Note that the specimens should not be taken within 5 to 6.3 cm of the outside<br />
edges of the slab. This is approximately 2 to 2.5 times the nominal top size of the aggregate<br />
used. Store approximately 3 kg of the wasted mix for the determination of the theoretical<br />
maximum specific gravity as described in section 6.<br />
6. CALCULATE THE AIR VOID CONTENT<br />
6.1 Weigh the dry, unwrapped, room-temperature-stabilized specimen. Record this<br />
as Mass in Air, A.<br />
6.2 Wrap the specimen in Parafilm so that it is completely watertight with no air<br />
bubbles between the Parafilm and the specimen. Use the minimum amount of Parafilm<br />
necessary. Weigh the specimen in air and record this as Mass in Air with Parafilm, B.<br />
6.3 Weigh the wrapped specimen suspended in water at 25°C (77°F), taking the<br />
reading as soon as the balance stabilizes. Record this as the Mass in Water with Parafilm, C.<br />
6.4 Determine the specific gravity of Parafilm at 25°C, or assume a value of 0.9.<br />
Record this as D.<br />
6.5 Calculate the bulk specific gravity of the specimen as follows:<br />
169
l i /l<br />
Gmb = . (1)<br />
B-Cwhere<br />
A = Mass of dry uncoated specimen in air, g<br />
B = Mass of Parafilm-coated specimen in air, g<br />
C = Mass of Parafilm-coated specimen in water, g<br />
D = Specific gravity of Parafilm at 25°C (77°F)<br />
G_ = bulk specific gravity<br />
6.6 Determine the theoretical maximum specific gravity, Gmm,in accordance with<br />
ASTM D 2041-78.<br />
6.7 Calculate the air void content as follows:<br />
Air Voids= [1-( Gmbll " lO0% (2)<br />
[ tG..)J<br />
7. CALCULATE THE QUANTITY OF BITUMINOUS MIX REQUIRED<br />
7.1 Measure the dimensions (height, length and width) of the compaction mold that<br />
will contain the compacted slab. Record this as H, L and W in dm.<br />
7.2 Determine the volume (V) of the mold in units of cm3.<br />
7.3 Determine the maximum specific gravity of the bituminous mix at the desired<br />
asphalt content in accordance with ASTM D 2041. Record this as Gram.<br />
7.4 Determine the target bulk specific gravity for the compacted slab based on the<br />
target air void content:<br />
Grab : Gmr a (1 _AV]100 J (3)<br />
where<br />
Gr,a, = target bulk specific gravity of the compacted slab<br />
%AV = target air voids of the compacted slab (percent)<br />
7.5 Determine the unit mass (density) of the compacted slab:<br />
170
P = Grab Pw<br />
(4)<br />
where<br />
p = unit mass of the compacted slab, kg/m 3<br />
Pw = unit mass of water, kg/m 3<br />
7.6 Determine the mass, M (in kilograms) of the compacted slab:<br />
M=pV<br />
7.7 Determine the mass of the aggregate required for compaction as shown below in<br />
equations 5 and 6. Equation 5 uses the asphalt content based on the dry mass of the<br />
aggregate, whereas equation 6 uses the asphalt content based on total mass of the mixture.<br />
M.g : (5)<br />
I +%AC<br />
I( )] 100<br />
: M [1- %ac] (6)<br />
[ loo j<br />
where<br />
M_r = total mass of aggregate, kg<br />
%AC = asphalt content<br />
7.8 Determine the mass of asphalt binder required for compaction as shown in<br />
equations 7 and 8 below. Equation 7 uses the asphalt content based on the dry mass of the<br />
aggregate, whereas equation 8 uses the asphalt content based on total mass of the mixture.<br />
MAC : M,,_<br />
[ %AC] (7)<br />
[_J<br />
[%AC] (8)<br />
MAc : M [_j<br />
where<br />
M,w = mass of asphalt binder, kg<br />
171
8. REPORT<br />
8.1 The report shall include the following information:<br />
8.1.1 Bituminous Mixture Description--bitumen type, bitumen content, aggregate<br />
type, aggregate gradation, and air void percentage.<br />
8.1.2 Mix and compaction temperatures, °C.<br />
8.1.3 Mass of specimen in air, g (A)<br />
8.1.4 Mass of specimen in air with Parafilm, g (B)<br />
8.1.5 Mass of specimen in water with Parafilm, g (C)<br />
8.1.6 Specific gravity of Parafilm (D)<br />
8.1.7 Bulk specific gravity, G,,_,<br />
8.1.8 Maximum specific gravity, G,,_<br />
8.1.9 Air void content of specimen, percent<br />
8.1.10 Dimensions of mold, cm<br />
8.1.11 Volume of mold, cm3<br />
8.1.12 Unit mass of compacted slab, kg/cm 3<br />
8.1.13 Mass of mix required for compaction, kg<br />
8.1.14 Mass of aggregate required for compaction, M_r (kg)<br />
8.1.15 Weight of asphalt required for compaction, MAc(kg)<br />
8.1.16 Time of mixing, minutes<br />
8.1.17 Time of compaction, minutes<br />
9. PRECISION<br />
9.1 A precision statement has not yet been developed for this test method.<br />
172
Figure 1. Rolling Wheel Compactor<br />
173
1<br />
RAMP,<br />
..:i!i!iiiii:i:i:i:i:i:i:i:!:i/ PLATFORM<br />
MOLD WALLS :_ MOLDBASE PLATE<br />
_liiiiiiliiiiiiiiiiiiiiiiiiiiiiiiiiii<br />
i_iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiil<br />
Figure 2. Schematic of Mold for Slab<br />
174
Figure 3. Preheating<br />
the Mold<br />
175
Standard Method of Test for<br />
Determining the Fatigue Life<br />
of Compacted Bituminous Mixtures Subjected<br />
to Repeated Flexural Bending<br />
<strong>SHRP</strong> Designation: M-0091<br />
1. SCOPE<br />
1.1 This method determines the fatigue life and fatigue energy of a bituminous<br />
mixture beam specimen subjected to repeated flexural bending until failure. The failure point<br />
is defined as the load cycle at which the specimen exhibits a 50% reduction in stiffness<br />
relative to the initial stiffness.<br />
1.2 The values stated in SI units are to be regarded as the standard.<br />
1.3 This standard may involve hazardous materials, operations and equipment. This<br />
standard does not purport to address all of the safety problems associated with its use. R is<br />
the responsibility of the user of this standard to establish appropriate safety and health<br />
practices and determine the applicability of regulatory limitations prior to use.<br />
2. APPARATUS<br />
2.1 Test System--The test system shall be capable of providing repeated sinusoidal<br />
loading at a frequency of between 5 and 10 Hz. The specimen shall be subjected to 4-point<br />
bending with free rotation and horizontal translation at all load and reaction points. Figure 1<br />
illustrates the loading conditions. The specimen shall be forced back to its original position<br />
(i.e., zero deflection) at the end of each load pulse. The test system or surrounding<br />
environment shall maintain the specimen at 20°C during testing.<br />
The test system shall be a closed-loop, computer-controlled system that, during each<br />
load cycle, measures the deflection of the beam specimen, computes the strain in the<br />
specimen, and adjusts the load such that the specimen experiences a constant level of strain<br />
on each load cycle. The test system should recQrd load cycles, the applied load and beam<br />
deflection, and compute the maximum tensile stress, maximum tensile strain, phase angle,<br />
stiffness, dissipated energy, and cumulative dissipated energy at load cycle intervals specified<br />
by the user.<br />
IThis standard is based on <strong>SHRP</strong> Product 1019.<br />
177
As a minimum,<br />
the test system should meet the following requirements:<br />
Load Measurement<br />
and Control<br />
Range: + 4.5 kN<br />
Resolution: 0.002 kN<br />
Accuracy: + 0.004 kN<br />
DispIacement Measurement and Control<br />
Range: _+_+ 5.0 mm<br />
Resolution: 0.00254 mm<br />
Accuracy: 5:0.005 mm<br />
Frequency Measurement and Control<br />
Range:<br />
Resolution:<br />
Accuracy:<br />
5 to 10 Hz<br />
0.005 Hz<br />
0.01 Hz<br />
Temperature Measurement and Control<br />
Resolution:<br />
Accuracy:<br />
0.25°C<br />
_+0.5°C<br />
2.2 Miscellaneous Apparatus:<br />
• epoxy for attaching nut to specimen<br />
• screw, nut, block assembly for referencing LVDT to neutral axis of<br />
specimen<br />
• jig for setting proper clamp spacing<br />
3. TEST SPECIMENS<br />
3.1 Compacted Bituminous Concrete Specimens--Specimens shall be sawn on all<br />
sides with a diamond blade from a slab or beam of bituminous mixture prepared by<br />
kneading compaction or rolling wheel compaction. Specimens shall be 381 + 6.35 mm in<br />
length, 50.8 + 6.35 mm in height and 63.5 + 6.35 mm in width.<br />
3.2 Measurement of Specimen Size--Measure the height and width of the specimen at<br />
three different points along the middle 90 mm of the specimen length. Report measurements<br />
to the nearest 0.025 ram. Average the three measurements for each dimension and report the<br />
averages to the nearest 0.25 rru_.<br />
178
3.3 Epoxy Nut to Neutral Axis of Specimen--Figure 2 illustrates a nut epoxied to<br />
the neutral axis of the specimen. Locate the center of a specimen side. Apply epoxy in a<br />
circle around this center point and place the nut on the epoxy such that the center of the nut<br />
is over the center point. Avoid applying epoxy such that it fills the center of the nut. Allow<br />
the epoxy to harden before moving the specimen.<br />
4. TEST PROCEDURE<br />
4.1 Stabilize Specimen to Test Temperature--If the ambient temperature is not 20°C,<br />
place the specimen in an environment which is at 20 + 1°C for 2 hours to ensure the<br />
specimen is at the test temperature prior to beginning the test.<br />
4.2 Specimen Setup--Refer to figures 3 and 4.<br />
The clamps should be open to allow the specimen to be slid into position. The jig is<br />
used to ensure proper horizontal spacing of the clamps: 119 mm center-to-center. Once the<br />
specimen and clamps are in the proper positions, close the outside clamps by applying<br />
sufficient pressure to hold the specimen in place. Next, close the inside clamps by applying<br />
sufficient pressure to hold the specimen in place.<br />
Figure 4 illustrates the connection of the screw/nut/block assembly and the LVDT<br />
such that beam deflections at the neutral axis will be measured. Attach the LVDT block to<br />
the specimen by screwing the screw into the nut epoxied to the specimen. The LVDT probe<br />
should rest on top of the block and the LVDT should be positioned and secured within its<br />
clamp so its reading is as close to zero as possible.<br />
4.3 Test Parameter Selection--The operator selects the following test parameters and<br />
enters them into the automated test program: deflection level, loading frequency and load<br />
cycle intervals at which test results are recorded and computed by the computer. The<br />
deflection level depends on the strain level desired. The loading frequency should be between<br />
5 and 10 Hz. The selection of load cycle intervals at which test results are computed and<br />
recorded is limited by the amount of memory available for storing data.<br />
4.4 Estimation of Initial Stiffness--Apply 50 load cycles at a constant strain of<br />
100-300 micro-in/in. Determine the specimen stiffness at the 50th load cycle. This stiffness<br />
is an estimate of the initial stiffness which will be used as a reference for determining<br />
specimen failure.<br />
4.5 Selection of Strain Level--The selected deflection level should correspond to a<br />
strain level such that the specimen will undergo a minimum of 10,000 load cycles before its<br />
stiffness is reduced to 50 % or less of the initial stiffness. A stiffness reduction of 50 % or<br />
more represents specimen failure. A minimum of 10,000 load cycles ensures the specimen<br />
does not decrease in stiffness too rapidly.<br />
4.6 Testing--After selecting the appropriate test parameters, begin the test. Monitor<br />
and record (if not automated) the test results at the selected load cycle intervals to ensure the<br />
179
system is operating properly.<br />
in stiffness, stop the test.<br />
When the specimen has experienced greater than 50% reduction<br />
5. CALCULATIONS<br />
5.1 The foUowing calculations shall be performed at the operator-specified load cycle<br />
intervals:<br />
5.1.1 Maximum Tensiie Stress (kN)<br />
300aP (1)<br />
°t- wh 2<br />
where<br />
a = L/3<br />
L -- the beam span, typically 356 mm<br />
P -- the load in kilonewtons<br />
w -- the beam width in millimeters<br />
h = the beam height in millimeters<br />
5.1.2 Maximum Tensile Strain (ram ram)<br />
_t = (126h)/( 3L2 - 4a2) (2)<br />
where<br />
6 = maximum deflection at center of beam, in mm<br />
L = length of beam between outside clamps, 356 mm<br />
5.1.3 Flexural Stiffness (kPa)<br />
s = (3)<br />
5.1.4 Phase Angle (deg)<br />
6 = 360fs (4)<br />
where<br />
f = load frequency, in Hz<br />
s = time lag between P_ and 8m_, in seconds<br />
5.1.5 Dissipated Energy (kPa) per cycle<br />
D = _wtetsin(q_) (5)<br />
180
5.1.6 Cumulative Dissipated Energy (kPa)<br />
i=?l<br />
ED, (6)<br />
i=1<br />
where<br />
Di<br />
= D for the z_ load cycle<br />
NOTE 1.--If data acquisition is automated, dissipated energy (D) cannot be calculated for every load cycle,<br />
due to memory limitations of the computer system. Therefore, dissipated energy must be plotted against load cycles<br />
for the particular load cycles at which data was collected (i.e., the load cycles selected by the operator) up to the<br />
load cycle of interest. The area under the curve represents the cumulative dissipated energy. See figure 5 for a<br />
typical dissipated energy versus load cycle plot.<br />
5.1.7 Initial Stiffness (kPa)--The initial stiffness is determined by plotting stiffness<br />
(S) against load cycles (N) and best-fitting the data to an exponential function of the form<br />
S = Ae bN (7)<br />
where<br />
e =<br />
A =<br />
b =<br />
natural logarithm to the base e<br />
constant<br />
constant<br />
Figure 6 presents a typical plot of stiffness versus load cycles. The constant A<br />
represents the initial stiffness.<br />
5.1.8 Cycles to Failure--Failure is def'med as the point at which the specimen<br />
stiffness is reduced to 50% of the initial stiffness. The load cycle at which failure occurs is<br />
computed by solving for N from equation 7, or simply<br />
NI,so= [ln(S;,5o/A)]/b (8)<br />
where<br />
S_.50 = stiffness, 50% of initial stiffness, in kPa<br />
SI,5o/A = 0.5, by definition<br />
181
5.1.9 Cumulative Dissipated Energy to Failure (kPa)<br />
i=I<br />
(9)<br />
NON 2.--It is not necessary to measure the dissipated energy for every load cycle; the computer program<br />
used to control the fatigue test will systematically determine the dissipated energy at specified load cycles during the<br />
test. The total dissipated energy to failure will be summarized as part of the computer output.<br />
6. REPORT<br />
6.1 The test report shall include the following information:<br />
6.1.1 Bituminous Mixture Description--bitumen type, bitumen content, aggregate<br />
gradation, and air void percentage.<br />
6.1.2 Specimen Length--millimeters, to four significant figures<br />
figures<br />
figures<br />
6.1.3 Specimen Height--millimeters, average as per section 3.2, to three significant<br />
6.1.4 Specimen Width--millimeters, average as per section 3.2, to three significant<br />
6.1.5 Test Temperature--average during test, to the nearest 1.0°C<br />
6.1.6 Test Results--table listing the following results (to three significant figures) for<br />
each load cycle interval selected by the operator:<br />
Cumulative<br />
Load Applied Beam Tensile Tensile Flexural Phase Dissipated Dissipated<br />
Cycle Load Deflection Stress Strain Stiffness Angle Energy Energy<br />
IIII I III I III<br />
kN mm kPa mm/mm kPa deg kPa kPa<br />
I JJ[ III I III I<br />
6.1.7 Plot of Stiffness versus Load Cycles--refer to figure 6 for typical plot<br />
6.1.8 Initial Flexural Stiffness--kPa, to three significant figures<br />
6.1.9 Cycles to Failure<br />
6.1.10 Cumulative Dissipated Energy to Failure--kPa, to three significant figures<br />
182
plot<br />
6.1.11 Plot of Dissipated Energy versus Load Cycles--refer to figure 5 for typical<br />
7. PRECISION<br />
7.1 A precision statement has not yet been developed for this test method.<br />
183
Load<br />
Load<br />
Specimen<br />
Specimen<br />
Clamp<br />
Reac_i°n l Reaction<br />
Return to<br />
Original<br />
Position<br />
Free Translation and Rotation<br />
F_gure 1. Load and Freedom Characteristics of Fatigue Test Apparatus<br />
184
Figure 2. Nut Epoxied to Neutral Axis of Specimen and LVDT Block Attached<br />
185
Hgure 3. Inserting Specimen into Device<br />
186
Figure 4. Nut/Block/Screw/LVDT<br />
Connection<br />
187
0.06<br />
.m-4<br />
0.04<br />
_0.02<br />
oo<br />
0.00 , , , ,,,,,, .... ,,,,, , , , ..... , .......<br />
10 10 2 10 a 10 4 10 _<br />
Number of Repetitions (N)<br />
Figure 5. Dissipated<br />
Energy versus Load Cycles (Repetitions)<br />
188
0<br />
OO<br />
£<br />
m<br />
-r"_<br />
mlO 5<br />
10 4 , [ 'T I I 1Jl)I "T_ _ I I I [11] T_ I 1 I II1 I --I L [ ITTII[ I ] ] I I'[-'[_<br />
i0 i0 2 i0 3 i0 _ i0 5 I0 6<br />
Number of Repetitions (N)<br />
Figure 6. Stiffness<br />
versus Load Cycles (Repetitions)<br />
189
Standard Method for<br />
Determining the Fracture Strength and Temperature<br />
of Modified and Unmodified Hot Mix Asphalt<br />
Subjected to Cold Temperatures<br />
<strong>SHRP</strong> Designation: M-0101<br />
1. SCOPE<br />
1.1 This method determines the tensile strength and temperature at fracture of<br />
compacted bituminous mixtures by measuring the tensile load in a specimen which is cooled<br />
at a constant rate while being restrained from contraction.<br />
1.2 The values stated in SI units are to be regarded as the standard.<br />
1.3 This standard may involve hazardous materials, operations and equipment. This<br />
standard does not purport to address all of the safety problems associated with its use. It is<br />
the responsibility of the user of this standard to establish appropriate safety and health<br />
practices and determine the applicability of regulatory limitations prior to use.<br />
2. APPARATUS<br />
2.1 Test System--A test system capable of cooling a bituminous mixture specimen at<br />
a constant rate while restraining the specimen from contraction and periodically measuring<br />
the tensile load and the specimen temperature from the beginning of the test to specimen<br />
failure.<br />
Figures 1 through 3 present diagrams of a closed-loop test system that is capable of<br />
performing the required testing. As the environmental chamber is cooled by periodic<br />
injections of liquid nitrogen, the specimen contracts. The computer monitors the output of the<br />
LVDTs and when the average displacement (relative to the original specimen position)<br />
becomes greater than 0.0025 inch (10 micro-strain), the computer sends a signal to the step<br />
motor and the motor applies a tensile load to the specimen until it stretches back to its<br />
original position. This process is repeated as the specimen is continually cooled. By<br />
restraining the specimen from contraction, tensile stress in the specimen increases until it<br />
exceeds the tensile strength of the specimen and the specimen fractures. Elapsed time,<br />
chamber and specimen surface temperature, displacement, and load are periodically measured<br />
and automatically recorded by the computer throughout the test.<br />
1This standardis basedon <strong>SHRP</strong>Product 1021.<br />
191
As a minimum,<br />
the test system, should meet the following requirements:<br />
Load Measurement<br />
Range:<br />
Resolution:<br />
Accuracy:<br />
0 to 23kN tension<br />
_< 0.044 kN<br />
± 0. 1% FuII ScaIe<br />
Displacement<br />
Measurement<br />
Range:<br />
Resolution:<br />
Accuracy:<br />
± 0.5 mm<br />
< 0.00125 mm<br />
± 0.1% Full Scale<br />
Displacement<br />
Control<br />
Operating Range: 150 m 435 mm<br />
Resolution: < 0.00125 mm<br />
Accuracy:<br />
< 0.005 mm<br />
Temperature<br />
Measurement<br />
Range: -50 to +25°C<br />
Resolution: < 0. i °C<br />
Accuracy:<br />
+_0.3°C<br />
Temperature<br />
Control<br />
Range: -50 to + 10°C<br />
Resolution: < 0.1 °C<br />
Accuracy:<br />
± 0.54°C<br />
2.2 Specimen Alignment Stand--A device capable of providing concentric and<br />
perpendicular alignment between the platens and the specimen, and of securing the specimen<br />
and platens while the epoxy sets (figure 4). True alignment is critical to obtaining meaningful<br />
test results. Therefore, not only must the alignment device provide true alignment but it must<br />
be supported in a level position.<br />
2.3 Miscellaneous Apparatus:<br />
• 150-ram diameter, 50-ram thick specimen platens<br />
• Two 6.35-.mm diameter, 457-ram-long threaded rods with 2 nuts each<br />
• Epoxy (Thermoset DC-80 or equivalent)<br />
192
NOTE.--The instructions herein for specimen preparation relate to Thermoset DC-80 made by Meyer<br />
Plastics, Inc. If another epoxy brand is used, its manufacturer should be contacted regarding proper mixing<br />
proportions, application and curing requirements.<br />
• Modeling clay<br />
• Duct tape<br />
• Plumb bob<br />
• Balance of 5 kg capacity and sensitive to 0.1 g, and spatula for<br />
proportioning and mixing epoxy components<br />
• Oven of 120°C capability<br />
• metal pans<br />
• spatula<br />
• gloves<br />
• solvent<br />
• 240-grit sandpaper for removing failed specimen ends from platens,<br />
cleaning platens, and providing a rough surface on platens to promote<br />
epoxy adhesion<br />
• U-joint clevises, clevis eyelets, and clevis pins<br />
3. TEST SPECIMENS<br />
3.1 Compacted Bituminous Concrete Specimens--Specimens shall be sawn on all<br />
sides with a diamond blade from a slab or beam of bituminous mixture prepared by kneading<br />
compaction or rolling wheel compaction. Specimens shall be 50 + 3.5 mm 2 square and<br />
250 _ 6.3 mm in length.<br />
3.2 Measurement of Specimen Size--Measure each width dimension of the specimen<br />
at the middle of the specimen length and at points on each side of the middle point. Report<br />
width measurements to the nearest 0.02 mm. Average the three measurements for each width<br />
dimension and report to the nearest 0.2 ram. Multiply the average width dimensions to obtain<br />
the average cross-sectional area of the specimen and report to the nearest 1 mm 2.<br />
3.3 Specimen Platen Preparation and Specimen Alignment--Platens shall be clean<br />
and free of all materials or films and shall be rough to promote adhesion of the epoxy. After<br />
cleaning the platens, sand the platen surface with a piece of 240-grit sandpaper to remove<br />
any remaining epoxy from prior tests and to provide a rough surface for epoxy adhesion.<br />
193
With the ink marker, trace diar_.etral lines across the top face of the bottom platen such that<br />
they connect the aligm'nent holes on opposite sides of the platen. Also trace lines<br />
longitudinally along each side of the specimen such that each line divides the side by its<br />
midpoint. Lines on the specimen and platen will be used to provide concentric alignment.<br />
Screw the specimen platens into the alignment stand. Adjust the position of the platens to a<br />
length approximately 25 mm ionger than the specimen length. Insert the threaded rods into<br />
holes on opposite sides of platens but do not tighten yet. Use the plumb bob to align the<br />
holes between the top and bottom platens.<br />
3.4 Epoxy Preparation--Obtain 50 + 5 g each of epoxy resin and epoxy hardener in<br />
a container suitable for mixing. Thoroughly mix the two epoxy components at a 1:1 ratio<br />
until a uniform color and consistency results.<br />
3.5 Epoxying Specimen to Platens--Apply a 3- to 6-ram thick film of epoxy over a<br />
50-mm diameter area on both the top and bottom platens in the specimen alignment stand.<br />
Place the specimen between the platens and carefully lower the top platen so that the<br />
specimen ends, epoxy and platens are in contact.<br />
Check the alignment of the specimen by comparing the marked lines on the sides of the<br />
specimen to the marked lines on the bottom platen. Rotate the specimen, if necessary, to<br />
achieve concentric alignment.<br />
Equally apply the remaining epoxy to the comers between the specimen sides and the platen<br />
faces, being careful not to disturb the position of the specimen. Build up the epoxy<br />
approximately 25 mm along the sides of the specimen (relative to the platen face). The<br />
buildup of epoxy is necessary to provide adequate adhesion between the specimen and the<br />
platen such that failure occurs in the middle portion of the specimen rather than at the<br />
specimen/platen interface.<br />
Again, check the alignment of the specimen by comparing the marked lines on the sides of<br />
the specimen to the marked lines on the bottom platen. Rotate the specimen, if necessary, to<br />
achieve concentric alignment.<br />
The specimen shall remain in the alignment stand for 4 to 24 hours to allow the epoxy to<br />
harden. The ambient temperature around the specimen should be 20°C to 25°C to obtain<br />
sufficient curing of the epoxy. Cooler temperatures will require longer cure periods.<br />
3.6 Pre-Cooling Specimen--After the epoxy has cured, tighten the nuts on the<br />
threaded rods with fingers only. Remove the specimen/platen assembly from the alignment<br />
stand and screw a clevis eyelet into the top platen. Hang the specimen/platen assembly from<br />
the eyelet in a 5°C _+2°C environment for 6 h prior to testing. By pre-cooling the<br />
specimen, the test can begin at a low temperature, thus reducing the total duration of the test.<br />
It has been determined that pre-cooling does not significantly affect the test results.<br />
194
4. TEST PROCEDURE<br />
4.1 Test Setup<br />
Connect the specimen/platen assembly to the top U-joint clevis by inserting the eyelet<br />
between the clevis opening, aligning the holes, and inserting a pin through the holes. Screw<br />
another eyelet into the bottom platen and similarly connect the bottom eyelet to the bottom<br />
U-joint clevis.<br />
Attach the two clamps used to secure the LVDTs to the bottom platen with nuts and screws.<br />
Attach the thermistors to the specimen with modeling clay. Place one thermistor each at the<br />
bottom end, the center, and the top end of the specimen, each on a different side of the<br />
specimen. The thermistors are used to measure the temperature of the specimen surface.<br />
Attach the cable of the resistance temperature device (RTD) to the middle portion of the<br />
specimen on a free side. Secure the cable with duct tape. The RTD is used in monitoring<br />
controlling the environmental cabinet temperature.<br />
and<br />
Attach the two clamps used to secure the invar rods to the top platen with nuts and screws.<br />
Insert the LVDTs into the bottom clamps and the invar rods into the top clamps. Make sure<br />
each rod and LVDT pair are aligned properly. Adjust the clamps to obtain proper alignment.<br />
After aligning the rod and LVDT, secure the clamps to the platens and secure the invar rod<br />
in the top clamp.<br />
Adjust the position of the LVDT in the bottom clamp such that its voltage output is near<br />
zero. This is necessary to ensure the LVDT operates in its linear range during the test.<br />
Sufficiently loosen the threaded rods attached on opposite sides of the platens.<br />
secure the environmental cabinet door, and begin the test procedure.<br />
Close and<br />
4.2 Testing<br />
Start the flow of liquid nitrogen to cool the environmental cabinet to 5°C (typical). Monitor<br />
the specimen surface temperature and wait until the average surface temperature is 5 + 1°C<br />
before applying the initial tensile load to the specimen.<br />
Apply an initial tensile load of 0.04 + 0.004 kN to the specimen by manually turning the<br />
hand-crank on the step-motor to raise the top platen.<br />
Start cooling the cabinet at a rate of 10°C _<br />
1°C per hour.<br />
Occasionally monitor the test outputs (environmental cabinet temperature, specimen<br />
temperature, elapsed time, specimen displacement, load) as the test progresses to ensure all<br />
instrumentation is functioning correctly and a valid test is being conducted.<br />
195
5. CALCULATIONS<br />
A_er the specime_ fails, perform<br />
the following calculations.<br />
5.1 Calculate the fracture strength to the nearest 5 kPa as follows:<br />
Fracture<br />
Stress = Pu:t/A<br />
wlaere<br />
Pu_t= ultimate tensile toad at fracture in kilonewtons<br />
A = average cross-sectional area of specimen in millimeters squared<br />
5.2 Calculate the sIope of the thermally induced stress curve as follows:<br />
Slope = fS/fT<br />
where<br />
fS = average change in stress along the linear portion of the curve just prior<br />
to failure, in kilopascals<br />
fiT = average change in temperature along the linear portion of the curve just<br />
prior to failure, in degrees Celsius<br />
6. REPORT<br />
The test report shall include the following information:<br />
6.1 Bituminous Mixture Description--bitumen type, bitumen content, aggregate<br />
gradation, and air void percentage.<br />
6.2 Time to Failure--hours:minutes:seconds<br />
0.1°C<br />
6.3 Specimen Temperature at Failure--average of 3 thermistor readings to the nearest<br />
6.4 Cross-Sectional Area of Specimen--average as per section 3.2, to the nearest<br />
lmm 2<br />
6.5 Ultimate Load at Failure--maximum tensile load, to the nearest 0.04 kN<br />
6.6 Fracture Strength--ldlopascals as per section 5.1, to the nearest 5 kPa<br />
6.7 Slope of the Thermally Induced Stress Curve--ldlopascals per degree Celsius as<br />
per section 5.2, to the nearest kPa<br />
196
6.8 Failure Description--location of break along specimen length and the nature of<br />
break (angular, flat, broken aggregate, etc.).<br />
197
Step Motor<br />
L,.._<br />
Loading Rod<br />
Swivel Jig<br />
LN2 _<br />
Ac<br />
Specimen<br />
End Platen<br />
Clamp<br />
lnvar Rod<br />
Environmental<br />
Chamber<br />
LVDT<br />
"_-:':-:i .........................<br />
_]<br />
Load Cell<br />
-: Thermisters<br />
F_gure 1. Schematic of Testing Apparatus<br />
198
Clamping ,..__ Shaft<br />
i.'' i Collar r-- "<br />
Epoxy<br />
-- AC Specimen _--<br />
(a) Front View<br />
(b) Side View<br />
Figure 2. Data Acquisition<br />
System<br />
199
ATHENA<br />
TEMPERATURECONTROLLER<br />
ii:!i:::i:i:i:::i:i:i:-:,¢iiiii!i:i:i:i:i:i:!:::_i<br />
LN2 (_ _' iiii:ii:iiiii:iii!ii_ii.%iii::'::::i:::i:i:ii:: RTD<br />
,..%o.%,.o°°.°°..°,°o°°°o ,°%°°°,o°*°°.%%°.%,<br />
t 1 "i:i'i:i:i:i:i:i:i';:!_ i':!_':':::::!_<br />
_eoo,=o__!ii_iiiiiiii!?i!iii!ii?<br />
Valve ,...........................................,<br />
so,eoo,, i_!ilii_'_ii_,_i_ii<br />
Valve<br />
-.:i:::-:!:i:!:!:!:!:!:!:!:?:i:!:!:!:i:i:.<br />
. _ I<br />
Environmental Circulating<br />
Chamber<br />
Fan<br />
F_gure3. Schematic of Temperature Control System<br />
2OO
AI<br />
LOAD CELL<br />
TRANSDUCER SIGNAL<br />
3421A DATA ACQUISITION<br />
CONDITIONER SC-SA<br />
rCONTROL UNIT<br />
_-- III CHANNEL #1 _ II CHANNEL #8<br />
I LVDT #1 m is CHANNEL#2 CHANNEL #6<br />
LVDT #2 I I -_ • CHANNEL #3 -_- • CHANNEL #7<br />
STEP {THERMISTER #1 I _ • CHANNEL#3<br />
MOTOR [THERMISTER#21 -_ • CHANNEL#4<br />
A<br />
I PC21 1 [THERMISTER #31 _'_ • CHANNEL#5<br />
[:::::: BUS DRIVER<br />
DATA 1<br />
COLLECTIONJ<br />
Figure 4. Schematic of Specimen Alignment Stand<br />
201
Standard Practice for<br />
The Laboratory Evaluation of<br />
Modified Asphalt Systems<br />
AASHTO Designation: PP51<br />
1. SCOPE<br />
1.1 This practice provides procedures for 1) evaluating the use of and the need for<br />
modified asphalt binders and paving mixes within the SUPERPAVE @mix design system, 2)<br />
for determining whether modified asphalt binders satisfy the Method for Performance-Graded<br />
Asphalt MP1 and 3) modified paving mixes satisfy the SUPERPAVE ®mix specification. It<br />
utilizes the performance-based asphalt binder and paving mix tests, specifications, and<br />
pavement performance prediction developed in the <strong>SHRP</strong> asphalt research program.<br />
1.2 This practice provides procedures for evaluating modified binders and modified<br />
paving mixes using performance-based tests and criteria, and for estimating their<br />
performance characteristics in pavement service.<br />
1.3 This practice can be used for the evaluation of modified asphalt binders that meet<br />
the requirements of MP1, aggregates, paving mixes or any combination of these. The<br />
practice has two main topics: modified asphalt binders and modified paving mixes. Distinct<br />
evaluation procedures for aggregate modifiers are not covered in this practice. Aggregate<br />
modification is covered under the topic of modified paving mixes.<br />
1.4 This practice provides for two distinct treatments of modified asphalt binder. A<br />
modified asphalt binder proposed for use in an asphalt concrete pavement may be directly<br />
evaluated. Alternatively, a modifier can be combined with a base asphalt cement to produce a<br />
modified binder which meets MP1.<br />
1.5 The values stated in SI units are to be regarded as standard.<br />
1.6 This practice may involve hazardous materials, operations, and equipment. It<br />
does not purport to address all of the safety problems associated with its use. It is the<br />
responsibility of whomever uses this practice to consult and establish appropriate safety and<br />
health practices and determine the applicability of regulatory limitations prior to use.<br />
1 This standard is based on <strong>SHRP</strong> Product P001.<br />
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2. REFERENCED DOCUM3ENTS<br />
2.1 AASHTO Standards<br />
MP1 Method of Test for Performance-Graded Asphalt Binder<br />
M92 Specification for Wire-Cloth Sieves for Testing Purposes<br />
PP1 Practice for Accelerated Aging of Asphalt Binder Using a Pressurized Aging Vessel<br />
PP6 Practice for Grading or Verifying the Performance Grade of an Asphalt Binder<br />
TP1 Method of Test for Determining the Flexural Creep Stiffness of Asphalt Binder Using<br />
the Bending Beam Rheometer<br />
TP3 Method of Test for Determining the Fracture Properties of Asphalt Binder in Direct<br />
Tension<br />
TP5 Method of Test for Determining Rheological Properties of Asphalt Binder Using a<br />
Dynamic Shear Rheometer<br />
T44 Method of Test for Solubility of Bituminous Materials in Organic Solvents<br />
T48 Method of Test for Flash and Fire Points by Cleveland Open Cup<br />
T164 Method of Test for Quantitative Extraction of Bitumen from Bituminous Paving<br />
Mixtures<br />
T166 Method of Test for Bulk Specific Gravity of Compacted Bituminous Mixtures<br />
T170<br />
Method of Test for Recovery of Asphalt from Solution by Abson Method<br />
T179 Method of Test for Effect of Heat and Air on Asphalt Materials (Thin-Film Oven<br />
Tes0<br />
T209 Method of Test for Maximum Specific Gravity of Bituminous Paving Mixtures<br />
T228<br />
T240<br />
Method of Test for Specific Gravity of Semi-Solid Bituminous Materials<br />
Method for Effect of Heat and Air on a Moving Film of Asphalt (Rolling Thin Film<br />
Oven Tes0<br />
T283 Resistance of Compacted Bituminous Mixture to Moisture-Induced Damage<br />
2O4
2.2 <strong>SHRP</strong> Documents<br />
B-006 Extraction and Recovery of Asphalt Cement for Rheological Testing<br />
B-007 Separation of Asphalts by Ion Exchange Chromatography<br />
B-008 Separation and Analyses of Asphalts by Size Exclusion Chromatography<br />
M-001 Measurement of Initial Asphalt Adsorption and Desorption in the Presence of Water<br />
(Net Adsorption Test)<br />
M-002 Preparation of Compacted Specimens of Modified and Unmodified Hot Mix Asphalt<br />
Test Specimens by Means of the <strong>SHRP</strong> Gyratory Compactor<br />
M-003 Determining the Shear and Stiffness Behavior Deformation Characteristics of<br />
Modified and Unmodified Hot Mix Asphalt with SUPERPAVE Shear Test Device<br />
M-004 Measurement of the Permanent Deformation and Fatigue Cracking Characteristics of<br />
Modified and Unmodified Hot Mix Asphalt<br />
M-005 Determining the Creep Compliance and Strength of Modified and Unmodified Hot<br />
Mix Asphalt Using Indirect Tensile Loading Techniques<br />
M-006 Determining the Moisture Susceptibility Characteristics of Compacted Bituminous<br />
Mixtures Subjected to Hot and Cold Climate Conditions<br />
M-007 Short- and Long-Term Aging of Bituminous Mixes<br />
M-008 Preparation of Test Specimens of Bituminous Mixtures by Means of Rolling Wheel<br />
Compaction<br />
M-009 Determining the Fatigue Life of Compacted Bituminous Mixtures Subjected to<br />
Repeated Flexural Bending<br />
P-002 Guide for Grading or Verifying the Performance Grade of a Asphalt Binder<br />
P-004 Volumetric Analysis of Compacted Hot Mix Asphalt<br />
P-005 Measurement of the Permanent Deformation and Fatigue Cracking Characteristics of<br />
Modified and Unmodified Hot Mix Asphalt<br />
P-00X<br />
Superpave Mix Design (Being Developed)<br />
P-00Y Guidelines for Asphalt Refiners and Suppliers (Being Developed)<br />
SUPERPAVE ® Mix Design Manual for New Construction and Overlays<br />
205
2.3 Other Documents<br />
2.3.1 National Aggregates Association Test Method A--Fine Aggregate Angularity<br />
2.3.2 Pennsylvania Test Method No. 621 (April 1987)--Determining the Percentage<br />
of Crushed Fragments in Gravel<br />
2.3.3 Task Force 31--Polymer Modified Asphalts, Joint Committee of AASHTO-<br />
AGC-ARTBA, Subcommittee on New Highway Materials (January 1991)--Guide<br />
Specifications for Polymer Modified Asphalt, Version 2.7.<br />
3. DEFINITIONS<br />
3.1 Modifier--a materiaI incorporated in hot mix asphalt (HMA) or other types of<br />
asphalt paving mixes in addition to the asphalt cement, aggregate and mineral filler, in order<br />
to control the development of pavement distresses and enhance overall pavement<br />
performance. Modifiers may be any organic or inorganic material of suitable manufacture,<br />
used in virgin or recycled condition, that is dissolved, dispersed or reacted in asphalt cement<br />
or HMA or coated on aggregate particles.<br />
3.2 Base Asphalt Binder--an unmodified asphalt cement used in the production of a<br />
modified asphalt binder. The performance grade of a base asphalt cement may be<br />
substantially different from that of an unmodified asphalt binder customarily used in a<br />
particular location.<br />
a particular<br />
3.3 Conventional Asphalt Binder--an unmodified asphalt cement customarily used in<br />
location.<br />
3.4 Type I Polymer Modified Asphalt Binder--a conventional asphalt cement to which<br />
styrene block copolymers have been added (Guide Specifications for Polymer Modified<br />
Asphalt).<br />
3.5 Type H Polymer Modified Asphalt Binder--a conventional asphalt cement to<br />
which styrene butadiene rubber (SBR) latex or neoprene latex has been added (Guide<br />
Specifications for Polymer Modified Asphalt).<br />
4. SUMMARY OF THE PRACTICE<br />
4.1 This practice presents a procedure for the laboratory evaluation of modified<br />
asphalt binder and paving mixes for HMA pavements. It utilizes the SUPERPAVE ®<br />
performance-based binder and paving mix tests, specifications, mix design system, and<br />
pavement performance prediction models. Materials are evaluated as a single component<br />
and/or as a multi-phase component in the final paving mix produced for roadway placement<br />
206
using the same SUPERPAVE ® performance criteria established for conventional (unmodified)<br />
materials.<br />
4.2 The selected modifiers are characterized by standard physical and chemical<br />
properties used to identify them for future reference. Modified materials are then<br />
characterized according to the SUPERPAVE ® performance-based specifications and mix<br />
design system, Any properties specifically intended for quality control of production or<br />
performance of the modified asphalt binder, aggregate, or paving mix are identified.<br />
4.3 The final choice of materials (modifier, base asphalt cement, and aggregate) is<br />
guided by reference to the criteria that led to the decision to use a modifier and to any<br />
restrictions on the availability of materials.<br />
NOTE 1.--The information required for the selection of modifiers for asphalts, aggregates or paving mixes<br />
will usually be provided by the modifier producer. However, it can also be obtained from the literature and by<br />
contacting other modifier users. The targeted pavement distress(es) should be indicated. The effect of the modifier on<br />
other pavement performance areas must also be considered in the selection process. This information and the<br />
historical pavement and laboratory performance will aid in determining whether a given modifier will address the key<br />
pavement problems in the targeted climatic and traffic conditions.<br />
NoTE 2.--The results of the characterization of each modified material should be compared with MP1<br />
criteria, historical data and the characteristics of conventional asphalt binders. Based on this comparison, if the<br />
expected pavement performance is acceptable, the evaluation should proceed to the next step (modified asphalt<br />
binder, aggregate, paving mix or pavement evaluation).<br />
4.4 If the expected performance is unacceptable at the completion of any step in the<br />
laboratory evaluation of a modifier, the modifier is rejected or the process is repeated with<br />
another modifier, base asphalt binder, or aggregate to optimize the formulation. The<br />
evaluation may also go forward to the next step, even if the properties and performance of<br />
the modified asphalt binder or paving mix are unfavorable, in order to develop additional<br />
data for making a final decision on the use of a candidate modifier.<br />
4.5 The cost of producing and placing the materials is estimated to aid in the<br />
decision regarding the use of the modified system. In addition, a simple analysis of the lifecycle<br />
cost of using the modified materials is made from the results of the SUPERPAVE ®<br />
performance-based mix tests and pavement performance prediction models, where<br />
appropriate, and compared to the use of conventional asphalt binders and paving mixes.<br />
4.6 The modified HMA production and laydown should be completed using only the<br />
equipment and procedures recommended by the modifier producer. The pavement should be<br />
produced in accordance with the material proportions and volumetric properties developed in<br />
the SUPERPAVE ®mix design.<br />
5. SIGNIFICANCE AND USE<br />
5.1 This practice presents detailed procedures for evaluation of modified asphalt<br />
binder, aggregate, and paving mix, singly or in combination. The laboratory tests used in<br />
207
this practice measure fundamental properties that directly govern the response of a pavement<br />
to load. From these data, pavement performance, in terms of the deveIopment of permanent<br />
deformation (ratting), fatigue cracking, and low-temperature cracking over the service tife of<br />
the pavement, is estimated. The influence of aging and water sensitivity on pavement<br />
performance is also explicitly considered.<br />
5.2 Use of this practice allows the evaluation and selection of a modified asphaIt<br />
binder, aggregate, or paving mixes on the basis of a required level of pavement performance<br />
under the present and predicted traffic, environmental, and structural conditions.<br />
6. MATERIALS SELECTION<br />
6.1 Select the modifier, base asphalt cement, and aggregate to satisfy the specific<br />
performance criteria that led to the decision to use a modifier. The performance criteria arise<br />
from the need to eliminate or reduce one or more pavement distresses or improve the overall<br />
performance or service life of the pavement. Consider the availability, compatibiIity, and<br />
cost of the requisite materials in the selection process.<br />
6.2 Modified asphaIt binder or paving mix are usually used because conventional,<br />
locally availabIe materials do not satisfy the SUPERPAVE ® specification for the site-specific<br />
traffic, environmental, and structural conditions. Choose a modifier for a base asphalt binder,<br />
aggregate, or paving mix after considering the recommendations of the modifier producer<br />
and historical performance data.<br />
NOTE 3.--Some convemional asphalt binders or aggregates may not be chemically or physically compatible<br />
with a modifier or may not develop the specific levels of performance expected from the use of the modifier. Any<br />
method recommended by the producer for screening asphalts or aggregates should be utilized to aid in the selection<br />
process. However, there may be cases where the objective is to improve the characteristics of a specific base asphalt<br />
cement and the evaluation of the modifier may be pursued even though the asphalt cement or aggregate is not the<br />
ideal candidate.<br />
6.3 Table 1 presents information required for the selection of modifiers for asphalt<br />
binders, aggregates or paving mixes. Obtain this information from the modifier producer, the<br />
highway literature, and contacts with other agencies using modifiers.<br />
6.4 Prepare "Fact Sheets" from the information called for in section 6.3 to assist in<br />
the selection of modifiers. The fact sheets shall include: the name of the modifier; any effects<br />
on material properties; restrictions; a description of the modifier; any special handling or<br />
production requirements. Identifythe targeted pavement distress(es) and note the effect of the<br />
modifier on other pavement performance areas. This information and the historical pavement<br />
and laboratory performance data will aid in determining if a particular modifier will address<br />
the key pavement problems identified for the proposed application and use.<br />
6.5 Measure the significant physical and chemical characteristics and specifications<br />
for the modifier, particularly the properties that are critical for monitoring the quality of the<br />
product. Obtain recommendations concerning the type of asphalts and aggregates that can or<br />
208
must be used with the modifier from the modifier producer. Also obtain unique or<br />
specialized procedures for determining asphalt or aggregate compatibility with the modifier.<br />
NOTE 4.--Chemical characterization of the modifier and the base asphalt binder may aid in determining the<br />
effect of modifier use on pavement performance. Chemical properties such as molecular weight and size,<br />
composition, association, and functionality are indicators of asphalt binder performance. Size exclusion<br />
chromatography, ion exchange chromatography, and infrared spectroscopy are key tools for determination of<br />
performance-related chemical properties of asphalt binder. A complete discussion and relevant experimental<br />
procedures are presented in the <strong>SHRP</strong> publication Guidelines for Asphalt Refiners and Suppliers.<br />
6.6 Characterize the base asphalt binder with the SUPERPAVE ® performance-based<br />
conditioning procedures and tests for asphalt binders (table 2). This information will allow<br />
comparison of the base asphalt binder with the modified asphalt binder using performancebased<br />
properties. Base the selection of the modifier on improved performance as indicated by<br />
the change in the binder performance grade achieved by modification, and on the<br />
accompanying change in the costs of HMA production and laydown.<br />
6.7 The bending beam rheometer characterizes asphalt binders by measuring creep<br />
stiffness at low temperatures. The dynamic shear rheometer measures the shear stiffness at<br />
high temperatures. The direct tension test characterizes the strain tolerance of the asphalt<br />
binder at low temperatures. The rolling thin film oven test (T240) and the thin-film oven test<br />
(T179) simulates short-term aging (HMA production). The pressurized aging vessel test<br />
simulates long-term aging that occurs in the pavement after construction.<br />
7. MODIFIED ASPHALT BINDERS AND PAVING MIXES<br />
7.1 General--Obtain information from the modifier producer concerning the<br />
equipment, procedures and amount necessary for the laboratory production of the modified<br />
asphalt binder, aggregates, or paving mixes. This information shall include health and safety<br />
data, special conditions for handling and storage, and any unique quality control parameters<br />
recommended by the producer. Pay particular attention to procedures and equipment not<br />
common to the HMA industry. Identify any special needs or problems prior to beginning the<br />
evaluation process.<br />
NoTE 5.--For example, there are several important special handling and storage conditions for sulfurextended<br />
asphalt. Any tank or silo in which sulfur-extended asphalt binder or HMA is stored must be carefully<br />
vented before opening to avoid exposure of workers to toxic hydrogen sulfide (H2S) or sulfur dioxide (SO_) gases. If<br />
access to such storage is required, workers must wear the correct level of protective clothing. Sulfur and asphalt<br />
binder must not be contacted or stored together at temperatures above 150°C to minimize formation of toxic gases.<br />
7.2 Modified asphalt binder--Production processes for modified asphalt binders<br />
depend greatly on the physical and chemical characteristics of the modifier and base asphalt<br />
binder. They may vary from simple, low-energy mixing, to high-shear blending that requires<br />
close control of time and temperature, to actual reaction of the component materials. At a<br />
minimum, achieve quality control during production by monitoring the appropriate<br />
performance-based theological properties listed in table 2. Other properties recommended by<br />
the modifier producer may also be measured periodically. Use the same physical, chemical<br />
209
and performance-based properties (table 3) used to characterize the base asphalt binder to<br />
evaluate and characterize the modified asphalt binder. Include any property critical to the<br />
performance of the modified asphalt binder, but not applicable to the conventional asphalt<br />
binders in the characterization.<br />
7.3 Modified Aggregate--Modified aggregate production may vary greatly depending<br />
on the characteristics of the modifier and the aggregate. The procedure may be just simple<br />
mixing or may involve a complicated coating process. Identify quality control methods by the<br />
modifier producer or process designer.<br />
7.4 Modified Paving Mix--Table 3 presents information necessary for the laboratory<br />
production and characterization of modified paving mixes. Use the same physical and<br />
performance-based tests used to characterize conventional paving mixes to characterize the<br />
modified paving mixes. Methods and procedures for the design of conventional and modified<br />
paving mixes are briefly presented in the sections 8.3 and 8.4 of this practice and in detail in<br />
the SUPERPAVE ®Mix Design Manual for New Construction and Overlays.<br />
80 LABORATORY EVALUATION OF MODIFIED ASPHALT BINDERS<br />
8.1 General--There are hundreds of potential modifiers that may change or alter<br />
asphalt binder properties. This practice is intended to provide a framework for the objective,<br />
quantitative evaluation of these candidate materials. It does not provide specific blending and<br />
preparation procedures. Develop these procedures in consultation with the producers of<br />
specific modifiers (note 6). Use the procedures listed in table 2 to evaluate modified asphalt<br />
binders. These procedures measure fundamental properties related to pavement performance,<br />
and they apply equally to modified and unmodified binders (note 7).<br />
NOTE 6.--Several test procedures presented in this section apply to specific types of modified asphalt<br />
binders. These procedures may also apply to other modifiers in present use or to novel materials that may be<br />
employed in the future. However, their applicability should be decided in consultation with modifier producers.<br />
NOTE 7.--MP1 grades binders on the basis on their performance capabilities at low (< -10°C) and high<br />
(> 520C) pavement temperatures. Grading is based on the properties of the asphalt binder aged to simulate a<br />
pavement service period of nominally five to ten years. Asphalt binders must meet the same specification property<br />
limits across the entire range of pavement service temperatures.<br />
8.2 Homogeneity<br />
8.2.1 Modified asphalt binders are generally multi-phase systems in which the<br />
modifiers are dispersed into the Iiquid asphalt cement phase. Many of these systems require a<br />
certain amount of incompatibility between the phases for the modifiers to provide any<br />
benefit, e.g., modifiers intended to disperse, not dissolve, in the base asphalt binder.<br />
8.2.2 Excessive incompatibility is not desirable for proper storage and handling.<br />
Therefore, a11modified systems should have a requirement for limiting separation of the<br />
modifier from the asphalt cement by measurement of rheological properties after aging of the<br />
modified binder in the rolling tt_ film oven test (T240).<br />
210
8.2.3 Sections 8.3 and 8.4 present specific separation tests for type I and type II<br />
polymer modified asphalt binders. Actual limits should be reported when sufficient data<br />
exists to support such criteria. A separation test for one type of material, however, may not<br />
provide appropriate data for other types. Consult modifier producers to determine appropriate<br />
separation tests and test limits for their particular materials.<br />
NOTE8.--These separation tests and the nomenclature are adapted from the Guide Specifications For<br />
Polymer Modified Asphalt.<br />
8.3 Separation Test for Type I Polymer Modified asphalt binder<br />
8.3.1 Evaluate a type I polymer modifier from asphalt cement during hot storage by<br />
comparing the dynamic shear stiffness of the top and bottom samples taken from a<br />
conditioned, sealed tube of polymer-modified asphalt binder. Condition the modifier by<br />
placing a sealed aluminum tube of polymer-modified asphalt binder in a vertical position in a<br />
165°C oven for 48 hours.<br />
8.3.2 Place the empty aluminum tube with its sealed end down in the rack. Carefully<br />
heat the sample until sufficiently fluid to pour. Avoid localized overheating. Strain the fluid<br />
sample through a 0.300-mm sieve conforming to M92. After thorough stirring, pour 50.0 g<br />
into the vertically held tube. Fold the excess tube over two times, crimp, and seal.<br />
NOTE9.--Aluminum tubes 25.4 mm in diameter by 139.7 mm long may be obtained from Sheffield<br />
Industries, P.O. Box 351, New London, CT 06320. Incidents have been reported regarding leakage of asphalt from<br />
the bottom of these tubes during the conditioning period. Other tubes may be required if this leakage is significant.<br />
8.3.3 Place the rack containing the sealed tubes in a 163 + 5°C oven. Allow the<br />
tubes to stand undisturbed in the oven for a period of 48 + 1 hour. At the end of the heating<br />
period, remove the rack from the oven and immediately place in the freezer at -5 + 5°C,<br />
taking care to keep the tubes in a vertical position at all times. Leave the tubes in the freezer<br />
for a minimum of 4 hours to completely solidify the sample.<br />
8.3.4 Upon removing the tube from the freezer, place the tube on a flat surface. Cut<br />
the tube into three equal length portions with appropriate tools. Place each section of tube<br />
into a separate 100 mL beaker in a 163 + 5°C oven until the modified binder is sufficiently<br />
fluid to remove the pieces of aluminum tube.<br />
8.3.5 After a thorough stirring, prepare specimens from the top and bottom samples<br />
for testing by TP5 (dynamic shear rheometer). Record and compare the shear stiffness of the<br />
top and bottom portions of the sample. Duplicate separation tests should be run. Test results<br />
shall be within 5 %.<br />
NOTE 10.--Other<br />
physical and chemical residue tests may be run at this time, if desired.<br />
8.4 Separation Test for Type H Modifiers<br />
8.4.1 This test is a simple qualitative test for compatibility of low-density polymers<br />
in asphalt.<br />
211
8.4.2 After a blend of polymer in unmodified asphalt binder has been prepared and is<br />
still at elevated temperature, pour enough of the blend into a clean 177 mL penetration tin to<br />
fill it to the formed roll on the cup (approximately 6 mm _ 0.25 mm from the top). Place<br />
the sample in a controlled temperature oven at 163 + 5°C for 15 to 18 hours. Remove the<br />
sample carefuIly from the oven without disturbing the surface and observe the sampIe. After<br />
the initial observation, a spatula may be used to gently probe the sample. While the sample is<br />
stii1 hot and within 5 minutes after removal from the oven, check the consistency of any<br />
surface layer and inspect for sludge on the bottom.<br />
8.4.3 Depending on the physical characteristics of the polymer and the compatibility<br />
of the particular asphalt cement/polymer modifier system, varying conditions will be noted.<br />
Report the condition of the modifier observed using the guidance provided in table 4.<br />
8.4.4 If these descriptions do not match the particular sample, note the exact<br />
phenomena encountered and retain the sample.<br />
8.5 Safety--Safety aspects of the modified asphalt binders are addressed in MP1 by a<br />
minimum Cleveland Open Cup flash point (T48) of 230°C. The modifier producer shall<br />
provide all other relevant safety _,:formation and requirements in the form of a Materials<br />
Safety Data Sheet and supporting documents.<br />
8.6 Purity--The base asphalt cement used in modified asphalt binders shaI1 meet a<br />
minimum requirement for solubility of 99 % by T44. This helps ensure that the polymermodified<br />
asphalt binder is not contaminated with unwanted mineral fines or fillers. The<br />
requirement is not placed on the blended, modified asphalt binder because many modifiers do<br />
not dissolve readily in the solvents presently used in the paving industry.<br />
8.7 Workability--Ideally, construction of asphalt concrete pavements with modified<br />
asphalt binder should not require unusual procedures in any part of the construction process.<br />
Because the formulation of modified asphalt binders has the potential to produce extremely<br />
high stiffness values, however, a high-temperature viscosity limit of 3 Pa.s at 135°C has<br />
been placed in MP1 to assure adequate pumpability of the modified binder at the HMA plant.<br />
This requirement may be waived if the modifier producer or HMA supplier warrants that the<br />
modified asphalt binder can be adequately pumped and mixed at temperatures that meet all<br />
applicable safety standards.<br />
8.8 Performance Testing of Modified Asphalt Binders--This section provides a<br />
method for determining the performance characteristics and performance grade of a modified<br />
asphalt binder according to the properties and Iimits contained in MPI. Comparison of these<br />
characteristics with those of conventional asphalt cements or of other modified asphalt<br />
binders commonly employed by a specifying agency permits an objective decision on the<br />
benefits of using a new modifier in a particular situation.<br />
8.8.1 Specimen Preparation--At least 400 g of the modified binder are required for<br />
evaluation. All test specimens should be prepared and blended (if required) in accordance<br />
with the producer's instructions. Select the initial concentration of modifier in the modified<br />
asphalt binder after consultation with the producer.<br />
212
8.8.2 Conditioning and Testing--Carry out conditioning and testing of the modified<br />
asphalt binder in accordance with section 6 or 7 of PP6.<br />
8.8.3 Evaluation--Evaluate the modified asphalt binder by comparing the results of<br />
the performance-based tests to the limits contained in MP1. This permits the capabilities of<br />
the modified asphalt binder to be objectively measured and gauged against those of<br />
conventional asphalt binders.<br />
8.8.3.1 Control the contribution of the asphalt binder to permanent deformation by<br />
specifying a minimum value for the stiffness parameter, G*/sin _ (= 1/J", the inverse of the<br />
loss compliance), at a maximum pavement design temperature. Correlate this parameter to<br />
that portion of the accumulated, non-recoverable deformation occurring in a pavement that is<br />
attributable to the asphalt binder. Comparison of the value of G*/sin _ for the modified<br />
asphalt binder with that of the base asphalt cement or of the conventional asphalt binder<br />
(under similar loading and temperature conditions), or with the limits in MP1, will indicate<br />
how well the modified asphalt binder will perform with respect to permanent deformation.<br />
8.8.3.2 Control the contribution of the asphalt binder to low temperature cracking by<br />
specifying limits for the creep stiffness, slope of the stiffness-time relationship, and the<br />
tensile strain at failure at test temperatures related to the lowest expected pavement design<br />
temperature. These properties affect the ability of the pavement to dissipate the tensile strains<br />
that result from rapid reductions in temperature or continual low-temperature cycling.<br />
Comparison of the measured values of these three properties for the modified asphalt binder<br />
with those of the base asphalt cement or the conventional asphalt binder (under similar<br />
loading and temperature conditions), or with the limits in MP1, will indicate how well the<br />
modified asphalt binder will perform with respect to low temperature cracking.<br />
8.8.3.3 Control the contribution of the asphalt binder to fatigue cracking by<br />
specifying a maximum value for the stiffness parameter, G'sin 6 (= G", the loss modulus),<br />
at the average pavement design temperature. This parameter is related to the contribution of<br />
the asphalt binder to the dissipation of energy in a pavement during each loading cycle.<br />
Comparison of the value of G'sin 6 for the modified asphalt binder with that of the base<br />
asphalt cement or of the conventional asphalt binder (under similar loading and temperature<br />
conditions), or with the limits in MP1, will indicate how well the modified asphalt binder<br />
will perform with respect to fatigue cracking.<br />
8.8.3.4 Aging may be divided into the changes which occur during construction<br />
(short term) and the changes which occur during the service life of the pavement (long term).<br />
Measure the binder property related to permanent deformation on asphalt binders aged by<br />
T240 or T179 to simulate changes that take place during construction. This helps limit the<br />
occurrence of early failure of the pavement due to rutting. Measure the binder properties<br />
related to fatigue cracking and low-temperature cracking on asphalt binders additionally aged<br />
by PP1 to simulate approximately 5 to 10 years pavement service. These types of distress<br />
tend to arise later in the service life of the pavement.<br />
213
NOTE 11.--The confounding effec_.of aging may be removed by also conducting the performance-based<br />
tests on unaged conventional asphalt binder and unaged modified asphalt binder. The test results for the aged and<br />
unaged binders can be compared to de'ermine the relative effects of aging on the different binders.<br />
NOTE 12.--T240 is the recommended procedure. Modified asphalt binder may phase separate or form skims<br />
during conditioning with T179 (TFOT); the results from subsequent test:_ngof this residue in TP5, TP1, and TP3<br />
may be distorted.<br />
8.8.3.5 The specifications incIude requirements related to the behavior of the asphalt<br />
binder during hot mix production and pavement construction. A minimum flash point is<br />
specified for safety. Viscosity ranges for mixing and compaction are identified so that<br />
equivalence compaction temperatures can be specified. These values should be noted for the<br />
modified asphalt binder and compared to those of the conventional asphalt binder to<br />
determine if any special procedures will be required for hot mix production and pavement<br />
construction. The effect of shear on the rheological properties of the modified asphalt binder<br />
at mixing and compaction conditions must also be evaluated. This should be determined by<br />
testing with the high-temperature rotational viscometer and the dynamic shear rheometer at<br />
temperatures and frequencies similar to those encountered during blending and mixing at the<br />
HMA plant.<br />
8.8.3.6 The results of the performance-based tests for the modified asphalt binder are<br />
compared to the MP1 specification values and the performance grade is determined. The<br />
comparison indicates the level of enhancement that the modified asphalt binder will produce<br />
in the targeted distress areas. This conclusion should then be compared with the level of<br />
enhancement promised by the producer and with any historical field performance data. Table<br />
5 presents the suggested minimum ratio of modified to conventional asphalt binder for MP1<br />
properties that should provide significant enhancement of binder performance. This table is<br />
for guidance only and should not be used for specification purposes.<br />
8.8.3.7 If the performance properties and grade of the modified asphalt binder are<br />
acceptable, initiate modified laboratory paving mix production and evaluation. Review the<br />
physical properties of the modified asphalt binder that reIate to production and pavement<br />
construction and identify any potential problems.<br />
8.8.3.8 If the performance properties and grade of the modified asphalt binder are<br />
ur_acceptable, halt the evaluation of the modifier. Review the results of the evaluation to this<br />
point to determine if the modification process was completed properly or if further<br />
optimization of the modification is warranted. For example, the level of modifier addition or<br />
the selection of a different base asphalt cement may have a large effect on the performance<br />
capabilities of the modified asphalt binder. If further optimization does not appear warranted,<br />
the evaluation should be terminated and the modifier rejected.<br />
NOTE 13.--The specifying agency may choose to further optimize the modified asphalt binder composition<br />
even though the results are favorable. It may also choose to proceed to the modified paving mix evaluation regardless<br />
of the results of the binder evaluation in order to develop additional data for a final decision on the use of the<br />
candidate modifier.<br />
214
9. LABORATORY EVALUATION OF AGGREGATE<br />
9.1 The SUPERPAVE ® mix design system requires measurement of the gradation,<br />
apparent specific gravity, bulk specific gravity, sand equivalent, Los Angeles abrasion,<br />
soundness, and deleterious material content of all aggregates, both unmodified and modified.<br />
Empirical guidelines are presented that relate several of these parameters to pavement<br />
performance. These tests are not considered performance-based for purposes of judging the<br />
effect of modification, and as such, are not covered by this practice. Modifications to the<br />
aggregate are evaluated strictly in terms of changes to the performance properties of the<br />
modified paving mix.<br />
10. LABORATORY EVALUATION OF PAVING MIXES<br />
10.1 The ultimate benefits of the use of modifiers are demonstrated by their effect on<br />
the performance characteristics of modified paving mixes. The SUPERPAVE ® system<br />
addresses the primary pavement distress modes of permanent deformation (rutting), fatigue<br />
cracking, and low-temperature cracking. It also accounts for the effects of aging and<br />
moisture in the development of these distresses. Environmental conditions and traffic are also<br />
explicitly considered.<br />
10.2 The asphalt binder makes up only about 5 weight percent of a paving mix. As a<br />
rule, the magnitude of the change in performance attributable to the modifier is smaller for<br />
the paving mix than for the asphalt binder. Moreover, the role of the asphalt binder, whether<br />
modified or not, in influencing pavement performance varies with the type of distress<br />
investigated. About 40% of the resistance of a paving mix to permanent deformation is<br />
attributable to properties of the asphalt binder; in contrast, binder properties can account for<br />
about 60% of a mix's resistance to fatigue cracking and as much as 90% of its resistance to<br />
low-temperature cracking.<br />
10.3 The SUPERPAVE ® accelerated mix performance tests and mix design system<br />
are the key tools for laboratory evaluation of modified paving mixes. As in the case of<br />
modified asphalt binders, the SUPERPAVE ®performance-based mix specification provides<br />
an objective measure against which the ability of specific modifiers to enhance pavement<br />
performance may be gauged.<br />
10.4 Performance Testing of Modified Paving Mixes--This section provides a method<br />
for determining the performance characteristics of modified paving mixes, comparing them<br />
with criteria contained in the SUPERPAVE ®performance-based mix specification, and<br />
estimating their influence on long-term pavement performance. Correlation of these<br />
performance characteristics with those of conventional paving mixes (or of other modified<br />
mixes commonly employed by the specifying agency) permits an impartial decision on the<br />
benefits of using a new modifier in a particular situation.<br />
NOTE 14.--The SUPERPAVE ® pavement performance prediction models were used to develop the<br />
SUPERPAVE ® mix specification limits. Since the mix design system incorporates accelerated performance tests that<br />
215
measure fundamental material properties _at govern pavement performance, the SUPERPAVE ® system is applicable<br />
to either standard asphalt-aggregate paving mixzs or modified asphalt-aggregate paving mixes.<br />
10.4.1 Specimen Preparation--Prepare all required cylindrical specimens of modified<br />
mix using the <strong>SHRP</strong> gyratory compactor in conformance with <strong>SHRP</strong> M-002. Blend or<br />
combine modifiers with the base asphalt cement, aggregate, or paving mix, as appropriate, in<br />
accordance with the producer's instructions.<br />
NOTE 15.--When required, prismatic beam specimens may be prepared in conformance with <strong>SHRP</strong> M-008<br />
(rclling wheel compaction) or other appropriate means.<br />
10.4.2 Conditioning and' Testing--Condition and test the modified mix in accordance<br />
with the SUPERPAVE ®Mix Design Manual for New Construction and Overlays and relevant<br />
procedures and methods referenced therein. Table 6 presents a summary of the conditioning<br />
procedures and performance-based test methods generally employed.<br />
10.4.3 Evaluation--Accomplish evaluation by estimating the performance of a<br />
pavement constructed with the modified paving mix. Make calculations using the pavement<br />
performance prediction algorithms in the SUPERPAVE ® software. This permits an objective<br />
comparison of the performance characteristics of the modified paving mix to the standard or<br />
conventional paving mix.<br />
10.4.3.1 Conduct laboratory aging of the modified paving mix principally to<br />
condition the specimens used in the performance-based mix tests in table 6. This conditioning<br />
simulates the short- and long-term aging that occurs during HMA production and pavement<br />
service. In addition, if the dynamic modulus of aged specimens is measured and compared<br />
with that of unaged specimens, the rate and degree to which the modified paving mix will<br />
age, compared to a conventional asphalt paving mix, can be estimated.<br />
10.4.3.2 Conduct moisture conditioning in the laboratory to identify candidate paving<br />
mixes that have an unacceptable moisture susceptibility. These mixes can then be eliminated<br />
or subjected to remedial treatment. Changes in tensile strength or dynamic modulus provide a<br />
direct measure of moisture susceptibility. Optionally, test the conditioned specimens in any of<br />
the performance-based mix tests to determine the effect of moisture on the development of<br />
specific pavement distresses.<br />
10.4.3.3 The contribution of the paving mix to permanent deformation is gauged by<br />
the results of <strong>SHRP</strong> M-003. _s simulates the high shear stresses that develop near the<br />
pavement surface at the edges of tires, and that lead to both lateral and vertical deformations.<br />
Estimate the rut depth after any selected number of ESALs (equivalent single axle loads of<br />
80 kN) from the number of shear repetitions (in the repetitive shear, constant height test)<br />
needed to reach an accumulated permanent strain of 5 %. Conduct this test at a test<br />
temperature related to the maximum expected pavement temperature. Evaluate the potential<br />
for catastrophic, tertiary creep in the pavement with the repetitive shear test at a field state of<br />
stress. Conduct this test for 4000 cycles at an effective temperature and stress state<br />
appropriate for the paving project. Finally, use the results of the uniaxial strain, simple<br />
216
shear, volumetric and frequency sweep tests in the SUPERPAVE ® software to estimate the<br />
development of rutting over the service life of the pavement.<br />
10.4.3.4 Estimate the contribution of the paving mix to low-temperature cracking<br />
from the results of the indirect tensile creep and failure tests. Determine the master stiffness<br />
curve and the maximum stress and strain at failure of the paving mix directly over the entire<br />
low temperature service range. These test results measure the ability of the pavement to<br />
dissipate the tensile strains that result from rapid reductions in temperature or continual lowtemperature<br />
cycling. They are used in the SUPERPAVE ® software to estimate the rate and<br />
extent of development of low-temperature cracking over the service life of the pavement.<br />
10.4.3.5 Estimate the contribution of the paving mix to fatigue cracking in the<br />
SUPERPAVE ® mix design system by a surrogate procedure. Conduct frequency sweeps with<br />
the <strong>SHRP</strong> shear device at temperatures between 4 and 20°C to develop the shear modulus<br />
and phase angle at intermediate service temperatures. Use stiffness values calculated from<br />
these data with tensile strength results from the indirect tensile failure test to estimate the<br />
course of crack initiation and propagation in the paving mix. Use the test results in the<br />
SUPERPAVE ® software to estimate the rate and extent of development of fatigue cracking<br />
over the service life of the pavement.<br />
NOTE 16.--The surrogate procedure employs a regression equation that estimates the number of cycles to<br />
crack initiation from the mix stiffness. This equation was developed principally from test results for unmodified<br />
paving mixes. It should be applied to the results from modified paving mixes with caution. In cases where a modifier<br />
is considered primarily as a means to control fatigue cracking, it is recommended that flexural beam fatigue tests be<br />
conducted in place of the surrogate procedure on the modified mix.<br />
10.4.3.6 Compare the results of the SUPERPAVE ® performance-based tests for the<br />
standard or conventional paving mix with the results for the modified paving mix. This will<br />
allow a direct estimate of the extent to which use of the modified paving mix will reduce the<br />
incidence of each pavement distress over the service life of the pavement. In cases where<br />
reliable historical records are available, this estimate can be verified by comparing the known<br />
pavement performance of the conventional paving mix with the predicted performance. A<br />
rudimentary estimate of the cost-benefit ratio of using the modified paving mix in place of<br />
the conventional paving mix can also be made from these comparative results and the first<br />
costs of the modified and conventional HMA. The exact details of this calculation will<br />
depend upon agency policies, e.g., whether maintenance and rehabilitation are scheduled on<br />
a periodic basis or triggered by a specific level of distress.<br />
10.4.3.7 If the estimated pavement performance of the modified paving mix and its<br />
cost-benefit ratio are favorable, modified pavement construction may be initiated at the<br />
discretion of the specifying agency. This may entail completion of a mix design for the<br />
modified mix in order to optimize its performance characteristics. The volumetric and<br />
engineering properties of the modified paving mix that relate to field control of HMA<br />
production and pavement construction should also be determined, and any potential problems<br />
identified to the HMA contractor and agency inspectors.<br />
217
10.4.3.8 If the estimated performance of the modified paving mix or its cost-benefit<br />
ratio are unacceptable, then the evaluation of this modifier can be abandoned or the<br />
evaluation repeated to optimize the selection of materials or the mix design.<br />
NOTE 17.--The specifying agency may choose to further optimize the modified paving mix even though the<br />
results are favorable. It may also choose to proceed to pavement construction regardless of the results of the<br />
mo:iified mix evaluation in order to develop additional data for a final decision on the use of the candidate modifier.<br />
11. THE SUPERPAVE ® MIX DESIGN SYSTEM<br />
11.1 The performance-based testing described in sections 8 and 10 may all be<br />
conducted, if desired, within the context of the SUPERPAVE ®mix design system. This<br />
system is founded on measurement of fundamental material properties of the asphalt binder<br />
and paving mix, and is fully applicable to unmodified and modified systems. It should be<br />
routinely employed to produce optimized mix designs incorporating those modifiers shown<br />
effective for enhancing pavement performance through the procedures in sections 8 and 10.<br />
11.2 The SUPERPAVE ® mix design system develops an initial mix design based on<br />
volumetric mix properties. TIEs design is then optimized on the basis of pavement<br />
performance estimates calculated from fundamental material properties of the trial paving<br />
mix.<br />
11.3 Only the volumetric design is required for low traffic levels. At intermediate<br />
traffic levels (typically 10 6 tO 107 total design ESALs), the volumetric design and a<br />
streamlined series of performance-based paving mix tests selected from those in table 6 are<br />
conducted. For high traffic levels, the volumetric design and the full set of accelerated<br />
performance tests summarized in table 6 are advised. The SUPERPAVE ® system provides<br />
unique specification guidelines and criteria for each level of mix design.<br />
11.4 For modifiers with established performance capabilities, the mix design system<br />
can be used alone to develop modified paving mixes with optimal performance<br />
characteristics. The comparative testing of conventional asphalt binders or paving mixes is<br />
not necessary.<br />
12. MODIFIED ASPHALT PAVEMENT EVALUATION<br />
12.1 Table 7 presents key information that should be developed to guide the<br />
production, construction, and evaluation of modified asphalt pavements. Information should<br />
be supplied by the modifier producer concerning the equipment and procedures necessary for<br />
the field production and construction of the modified asphalt pavements. Any atypical HMA<br />
operations should be carefully reviewed jointly with the HMA contractor and the modifier<br />
producer. This will help identify any potential operational problems or special equipment<br />
needs. This information must include health and safety data, conditions for handling and<br />
storage of the modified asphalt binder and paving mix, and special field control requirements<br />
tc ensure that the plant mix will provide the expected performance.<br />
218
12.2 The HMA plant should produce the mix according to the parameters developed<br />
in the SUPERPAVE ®mix design discussed in section 8.4. The plant mix should be sampled<br />
and compared to the job mix formula developed in the mix design. In addition, and at the<br />
discretion of the specifying agency, modified asphalt binder and paving mix samples may be<br />
tested in accordance with the performance-based binder and mix tests used in the laboratory<br />
evaluation. This will ensure conformance of the plant-produced mix with the job mix<br />
formula.<br />
12.3 The construction of the modified asphalt pavement should follow normal<br />
practice except where special procedures are required by the modifier producer or from the<br />
results of the laboratory evaluation. For example, the equiviscous temperature for compaction<br />
may be different than for conventional asphalts binders.<br />
12.4 The compacted pavement should be evaluated for the key physical properties<br />
identified by the mix design procedure. At the discretion of the specifying agency, core<br />
samples or slabs may be taken and tested according to the SUPERPAVE ® performance-based<br />
binder and mix tests used in the laboratory evaluation and mix design. This will help ensure<br />
that the level of compaction is satisfactory and that the actual pavement performance will be<br />
commensurate with the mix design predictions.<br />
12.4.1 Evaluate the completed modified asphalt pavement initially by comparing the<br />
results of the performance-based tests of the pavement samples with the results of the<br />
laboratory evaluation and with the relevant mix specification. Compare the properties of the<br />
completed pavement with those of standard HMA pavements. Use the SUPERPAVE ®<br />
performance prediction models in the SUPERPAVE ® software to predict the expected<br />
pavement life based on the actual pavement properties.<br />
12.4.2 Long-term evaluation of the modified asphalt pavement requires the periodic<br />
monitoring of the pavement's performance and properties. It may be necessary to sample the<br />
pavement periodically and determine the performance-based properties to assess real-world<br />
effects of aging, traffic, and the environment on pavement performance. This will also<br />
facilitate the further validation and calibration of the SUPERPAVE ® prediction models. The<br />
best way to manage this task is through a good pavement management system (PMS).<br />
12.5 The actual cost of constructing the modified asphalt pavement should be<br />
determined and recorded in the PMS for future evaluation and life-cycle cost analysis. A lifecycle<br />
cost estimate should be based on the predicted life of the modified asphalt pavement as<br />
determined from actual pavement data and the actual cost of construction. This estimate<br />
should be updated periodically when pavement performance data and/or performance-based<br />
laboratory data is received from field samples. This cost and performance data should be<br />
compared to those of conventional asphalt pavements in similar service.<br />
12.6 The evaluation will be complete when the service life of the pavement is<br />
reached and the final performance and costs can be compared with predicted values and<br />
conventional systems. The value of the modifier in all likelihood can be established sooner if<br />
significant differences in performance are noted early in the life of the pavement.<br />
219
13. REPORT<br />
13.1 The report on the laboratory evaluation of the modifier system may include the<br />
following:<br />
13.1.1 name, concentration(s)0 and characterization i_ormation for the modifier<br />
recommended;<br />
13.1.2 mixing proced_ares, equipment, and hazards involved in the handling of the<br />
modifier;<br />
13.1.3 results of performance-based tests of a11materials;<br />
13.1.4 results of SUPERPAVE ® mix design procedure including final job mix<br />
formula;<br />
13.1.5 cost and performance comparison of the modified system with the unmodified<br />
system.<br />
14. KEY WORDS<br />
Aggregate, asphalt, characterization, field control, mix design, modifier, performance,<br />
performance-based, SUPERPAVE ®.<br />
220
Table 1. Modifier<br />
Selection and Characterization<br />
Selection<br />
• Target pavement distress(es)<br />
• Effect on other performance areas<br />
• Historical performance (laboratory and Field)<br />
• Health and safety data<br />
• Handling and storage requirements<br />
• Production procedures<br />
• Construction (laydown) procedures<br />
• Asphalt recommendations or requirements<br />
• Aggregate recommendations or requirements<br />
Characterization<br />
• Physical properties<br />
• Chemical properties<br />
• Quality control properties<br />
• SUPERPAVE e performance characteristics of<br />
modified asphalt binders and paving mixes<br />
Table 2. Performance-Based Binder Conditioning Procedures and Tests<br />
Procedure Measured Properties Pavement Distress<br />
TP5 high-temperature shear stiffness permanent deformation<br />
fatigue cracking<br />
TP1 low-temperature creep stiffness low-temperature cracking<br />
TP3 stress, strain, and energy to failure low-temperature cracking<br />
T240 mass loss and change in shear and creep short-term aging<br />
stiffness<br />
PP1 change in shear and creep stiffness long-term aging<br />
221
Table 3. Modified Asphalt Paving Mix Laboratory Production and Characterization<br />
[ 1| U<br />
Laboratory Production<br />
Recommendation from the Modifier Producer<br />
Equipment<br />
Procedu::es<br />
HealL%and Safety Information<br />
Quality Control Parameters and Test Methods<br />
Storage and Procedures<br />
Mix Design Procedures<br />
Producer Information<br />
SUPERPAVE ® Mix Design Manual<br />
Characterization<br />
Physical Properties (Developed in Mix Design Procedure)<br />
oVoids in the Mineral Aggregate<br />
*Air Voids<br />
*Voids Filled with Asphalt<br />
*Asphalt Binder Content<br />
Chemical Properties<br />
*Moisture Sensitivity<br />
*Effect of Aging<br />
Performance-Based Tests and Material Properties<br />
*Permanent Deformation (<strong>SHRP</strong> Shear Test)<br />
*Low-Temperature Cracking (Indirect Tensile Test)<br />
*Fatigue Cracking (Flexural Beam Fatigue Test)<br />
Table 4. Criteria for Type II Separation<br />
Test<br />
LI<br />
i<br />
Observation<br />
Report<br />
Homogeneous, no skinning or sludge Homogenous<br />
Slight polymeric skin at edges of cup Slight Edge Skinning<br />
Thin polymer skin on entire surface<br />
Thin Total Skinning<br />
Thick polymer skin (_> 1 ram) on entire Thick Total Skinning<br />
surface<br />
No surface skinning but thin sludge at<br />
bottom of container<br />
Thin Bottom Sludge<br />
No surface skinning but thick (> 6 mm) Thick Bottom Sludge<br />
sludge at bottom of container<br />
I IIIII I L II I I III IIIII I<br />
222
Table 5. Guidelines for Binder Modification<br />
I<br />
Binder Specification Suggested Ratio<br />
Property (Modified/Unmodified Binder)<br />
G*/sin _ >_ 2.5<br />
G'sin 6 < 0.7<br />
S -< 0.7<br />
m -> 1.2<br />
Table 6. Performance-Based Laboratory Mix Tests and Conditioning Procedures<br />
Pavement Equipment & Test Measurement<br />
Distress<br />
Permanent <strong>SHRP</strong> Shear Test Device: • Dilatancy<br />
Deformation • Uniaxial Strain Test • Accumulation of Permanent Strain<br />
• Volumetric Test • Stiffening under Conf'ming Stress<br />
• Simple Shear Test • Tertiary Creep<br />
• Frequency Sweep • Shear Modulus<br />
• Repetitive Shear Test at Constant Height • Phase Angle<br />
• Repetitive Shear Test at a Field State of Stress<br />
Low Indirect Tensile Test Device: • Creep Compliance<br />
Temperature • Indirect Tensile Creep Test • Tensile Strength<br />
Cracking • Indirect Tensile Failure Test<br />
Fatigue Simple Shear Test Device: • Shear Modulus<br />
Cracking • Frequency Sweep • Phase Angle<br />
(Surrogate Indirect Tensile Test Device: • Tensile Strength<br />
Method) • Indirect Tensile Failure Test<br />
Fatigue Flexural Beam Fatigue Device: • Cycles to Beam Failure<br />
Cracking • Constant Strain Flexural Fatigue at 20 °C<br />
(Referee<br />
Method)<br />
Water AASHTO T283: • Change in Tensile Strength<br />
Sensitivity • Tensile Strength in Dry and Wet Condition<br />
OF<br />
or<br />
Environmental Conditioning System:<br />
• Dynamic Modulus in Dry and Wet Condition • Change in Dynamic Modulus<br />
Aging--Short Forced Draft Oven Aging of Loose Mix: • Change in Dynamic Modulus<br />
Term • Dynamic Modulus in Unaged and Aged<br />
Condition<br />
Aging--Long Forced Draft Oven Aging of Compacted Mix: • Change in Dynamic Modulus<br />
Term • Dynamic Modulus in Unaged and Aged<br />
Condition<br />
223
Table 7. Modified Asphalt Pavement Production,<br />
Characterization, aud Evaluation<br />
Construction,<br />
[1 il Ill<br />
Pavement Production and Construction<br />
Recommendat'ons from the Modifier Producer<br />
Equipment<br />
Procedures<br />
Health and Safety Information<br />
Quality Controi Parameters and Test Method<br />
Storage and Handling Procedures<br />
Mix Design Procedures<br />
Producer's Recommendations<br />
SUPERPAVE ® Mix Design System<br />
Characterization (Production and Cores)<br />
Volumetric Properties (Developed in Mix Design Procedure)<br />
• Voids in the Mineral Aggregate<br />
• Air Voids<br />
• Voids Filled with Asphalt<br />
• Asphalt Binder Content<br />
Performance-Related and Performance-Based Properties<br />
• Aging<br />
• Moisture Sensitivity<br />
• Permanent Deformation<br />
• Low-Temperature<br />
• Fatigue Cracking<br />
Evaluation<br />
Cracking<br />
<strong>SHRP</strong> Performance-Based Specifications<br />
Comparison with Conventional Paving Mixes<br />
Historical Performance Data (Lab and Field)<br />
Pavement Management System<br />
Cost Analysis<br />
I<br />
II<br />
224
Standard Practice for<br />
Grading or Verifying the Performance Grade<br />
of an Asphalt<br />
Binder<br />
AASHTO Designation: PP61<br />
1. SCOPE<br />
1.1 This practice describes the testing required to determine the performance grade of an<br />
asphalt binder. It presents two approaches. In the first, the performance grade of an unknown<br />
asphalt binder is determined. In the second, the nominal performance grade of an asphalt<br />
binder is verified. It also provides an estimate of the time required to complete a single test<br />
sequence.<br />
1.2 The values stated in SI units are to be regarded as standard.<br />
1.3 This practice may involve hazardous materials, operations, and equipment. This<br />
practice does not purport to address all of the safety problems associated with its use. It is<br />
the responsibility of the user of this practice to establish appropriate safety and health<br />
practices and determine the applicability of regulatory limitations prior to use.<br />
2. REFERENCE DOCUMENTS<br />
2.1 AASHTO Documents:<br />
MP1 Method of Test for Performance-Graded Asphalt Binder<br />
PP1 Practice for Accelerated Aging of an Asphalt Binder Using a Pressurized Aging<br />
Vessel<br />
T48 Method for Flash and Fire Points by Cleveland Open Cup<br />
T179 Method for Effect of Heat and Air on Asphalt Materials (Thin-Film Oven Test)<br />
T240 Method for Effect of Heat and Air on a Moving Film of Asphalt (Rolling Thin<br />
Film Oven Test)<br />
TP1 Method of Test for Determining the Flexural Creep Stiffness of an Asphalt Binder<br />
Using the Bending Beam Rheometer (BBR)<br />
TP3 Method for Determining the Fracture Properties of an Asphalt Binder in Direct<br />
Tension (DT)<br />
TP5 Method of Test for Determining R_heological Properties of Asphalt Binder Using a<br />
Dynamic Shear Rheometer (DSR)<br />
1This standard is based on <strong>SHRP</strong>ProductP002.<br />
225
2.2 ASTM Documents:<br />
D 4402 Measurement of Asphalt Viscosity Using a Rotational Viscometer<br />
3. SUMMARY OF THE PRACTICE<br />
3.1 The tank sample of asphalt binder is tested to determine the flash point in °C<br />
(T48), viscosity at I35°C (D 4402), shear modulus (G*) and phase angle (6) (TP5).<br />
3.2 The asphalt binder is aged in the rolling thin film oven (T240) or the thin film<br />
oven (TI79), and the residue is tested to determine the mass loss (T240 or T179), the shear<br />
modulus (G*), and phase angle (tS) (TP5).<br />
NOTE 1.--T240 is the recommended procedure. Modified asphalt binders may phase separate or form skims<br />
during conditioning with T179 (TFOT); the results from subsequent testing of this residue in TP5, TP1, and TP3<br />
may be distorted.<br />
3.3 The residue from the rolling thin film oven or thin film oven is aged in the<br />
pressurized aging vessel (PP1). This residue is tested to determine the shear modulus (G*)<br />
and phase angle (6) (TP5), creep stiffness (S) and slope (m) of the log creep stiffness versus<br />
log time relationship at 60 seconds (TP1), the failure spain in direct tension (TP3), as<br />
necessary, and physical hardening measured by creep stiffness (S) and slope (m) of the log<br />
creep stiffness versus log time relationship at I and 24 hours (TP1).<br />
3.4 Based on these test results, the asphalt binder is graded according to MP1.<br />
4. SIGNIFICANCE AND USE<br />
This practice describes the testing required for grading or verifying the performance grade<br />
of an asphalt binder according to MP1.<br />
5. ESTIMATED TIME NECESSARY FOR TESTING<br />
For both grading and verification, if the analysis is started at the beginning of a morning<br />
work shift, all testing and analysis should be completed during the afternoon of the next<br />
day. This schedule provides the 20 hours needed for PAV conditioning. (It takes 1<br />
additional day to collect the physical hardening data as 24 hours of conditioning are<br />
required at the lowest grading test temperature to determine the extent of physical<br />
hardening.) Of course, samples can be aged and analyzed in parallel, and the productivity of<br />
the laboratory increased. For the purpose of this document, however, analysis of a single<br />
asphalt binder will be discussed.<br />
226
6. TEST PROCEDURE FOR GRADING AN UNKNOWN ASPHALT BINDER<br />
6.1 Prepare samples and test specimens using the procedures specified in the test<br />
methods performed. In the case where the grade of the asphalt binder is unknown,<br />
approximately 400 g of unaged asphalt binder is required to complete the tests with the<br />
necessary replicates.<br />
6.2 Begin conditioning asphalt binder in the rolling thin film oven (RTFO) or thin<br />
film oven (TFO). Condition a sufficient amount of asphalt binder depending on the type<br />
and number of tests to be performed.<br />
NOTE 2.--Two BBR beams requiring PAV material are needed at each test temperature. In addition, four<br />
DT specimens requiring PAV material may also be needed at each test temperature. A minimum of two test<br />
temperatures will be required. Approximately 200 g of RTFO or TFO residue will be required.<br />
6.3 Perform the DSR test (TP5) on the original asphalt binder beginning at 58°C,<br />
and increase or decrease the test temperature at 6.0°C increments until a value for<br />
G*/sin 5 < 1.00 kPa is obtained. The highest test temperature where the value for G*/sin 5<br />
is _>1.00 kPa determines the starting performance grade (PG).<br />
NOTE 3.--For<br />
grade is PG 58-.<br />
example, if G*/sin 5 is 0.6 kPa at 64°C and 1.2 kPa at 58°C, the starting asphalt binder<br />
6.4 Determine the flash point on a sample of original binder using T48. The flash<br />
point must be greater than 230°C to meet the requirements of MP1.<br />
6.5 Determine the viscosity of the original asphalt binder at 135°C using ASTM<br />
D 4402. The viscosity must not exceed 3 Pa.s to meet the requirements of MP1.<br />
6.6 After the RTFO test (T240) or TFO test (T179) is complete, determine the mass<br />
loss of the original asphalt binder. The mass loss must be _ 2.20 kPa. Choose the lower PG in cases where the test values in<br />
sections 6.3 and 6.8 give conflicting grades.<br />
6.9 Age a sufficient quantity of RTFO or TFO residue in the PAV (PP1). Use an<br />
aging temperature of 90°C for starting grades PG 46-x and 52-x binders, and 100°C for<br />
starting grades PG 58-x and higher. A PAV temperature of 110°C is to be used in<br />
simulating desert environments.<br />
227
NOTE 4.--Two BBR beams (requiring PAV material) are required at each test temperature. In addition,<br />
four DT samples may also be needed at each test temperature. A minimum of two test temperatures wilI be<br />
required.<br />
6.10 Complete steps 6.1 through 6.9 during the first day of testing. This will allow<br />
further testing to begin on the second day, when the PAV procedure is complete.<br />
6.11 At the conclusior_ of the PAV procedure, carefully remove the residue from the<br />
vessel and combine individual pans of the same aged asphalt binder. Prepare two bending<br />
beam specimens for each test temperature according to TP1. Retain sufficient residue to<br />
prepare four direct tension specimens for each test temperature if required.<br />
6.12 Perform the DSR test (TP5) on the PAV residue. Begin at a test temperature<br />
of 16°C for PG 52; 19°C for PG 58; 22°C for PG 64; and 28°C for PG 70, unless there is<br />
other information to suggest the temperature at which G'sin 8 is < 5000 kPa. Decrease or<br />
increase the test temperature at 3.0°C increments until the value for G'sin 8 exceeds<br />
5000 kPa.<br />
6.13 Determine the beginning test temperature for the BBR test (TP1) on the PAV<br />
residue from table 1 of MP1. Use the starting PG determined in section 6.3 and the lowest<br />
temperature from section 6.12 where the value for G'sin 8 did not exceed 5000 kPa, unless<br />
there is other information to suggest the temperature at which the stiffness is < 300.0 MPa,<br />
and the slope m is > 0.300.<br />
6.14 Test pairs of BBR specimens according to TP1. Begin at the test temperature<br />
selected in section 6.13 and increase at 6.0°C increments, until a stiffness and slope meeting<br />
the requirements of MP1 are obtained. Test fresh BBR specimens at each temperature.<br />
Determine the extent of physical hardening, report the creep stiffness (S) and the slope (m)<br />
of the log creep stiffness versus log time relationship measured at 1 and 24 hours. Prepare<br />
two sets each of two BBR specimens of original asphalt binder. Test one set after 1 hour of<br />
conditioning and the second set after 24 hours of conditioning. The latter is conducted at<br />
the lowest grading test temperature (Tmi_+ 10°C).<br />
6.15 Certain asphalt binders may satisfy the MP1 slope requirement at substantially<br />
lower temperatures than they satisfy the stiffness requirement. If the creep stiffness is<br />
between 300 and 600 MPa at a test temperature at which the slope (m) is > 0.300, it may<br />
be possible to satisfy the DT (TP3) failure strain requirement in lieu of the creep stiffness<br />
requirement. Test four DT specimens according to TP3 at the test temperature at which m ><br />
0.300, and determine if the failure strain is > 1.0%.<br />
6.16 If the failure strain is < 1.0%, test additional sets of four DT specimens.<br />
Increase the test temperature in 6.0°C increments until a failure strain > 1.0% is obtained.<br />
Determine the test temperature at which m > 0.300 and the creep stiffness is < 300.0 MPa,<br />
or, if the creep stiffness is between 300.0 and 600.0 MPa, the failure strain is > 1.0%.<br />
6.17 Using the results of steps 6.12 through 6.16, determine the final grade of the<br />
asphalt binder.<br />
228
7. TEST PROCEDURE FOR VERIFYING THE NOMINAL GRADE OF AN<br />
ASPHALT BINDER<br />
7.1 Prepare samples and test specimens using the procedures specified in the test<br />
methods performed. In the case where the grade of the asphalt binder is being verified,<br />
approximately 250 g of unaged asphalt binder is required to complete the tests with the<br />
necessary replicates.<br />
7.2 Begin conditioning asphalt binder in the rolling thin film oven (RTFO) or thin<br />
film oven (TFO). Condition a sufficient amount of asphalt binder depending on the type<br />
and number of tests to be performed.<br />
NOTE 5.--Two BBR beams that require PAV material are needed. In addition, four DT specimens<br />
requiring PAV material may also be required. Only one test temperature will be required. Approximately 100 g of<br />
RTFO or TFO residue will be required.<br />
7.3 Perform the DSR test (TP5) on the original asphalt binder at the test<br />
temperature indicated by the high-temperature grading designation. For example, test a PG<br />
70-16 asphalt binder at 70°C. The value for G*/sin 8 must be _ 1.0 kPa to meet the<br />
requirements of MP1.<br />
NOTE 6.--This step verifies the starting PG. For example, if G*/sin 8 _> 1.00 kPa at 58°C, the high<br />
temperature grading designation for the asphalt binder is PG 58-.<br />
NOTE 7.--If the asphalt binder fails to meet the requirements of MP1 for the grade at which it has been<br />
designated, it may be treated as a binder of unknown grade and tested according to section 6.<br />
7.4 Determine the flash point on a sample of original binder using T48. The flash<br />
point must be greater than 230°C to meet the requirements of MP1.<br />
7.5 Determine the viscosity of the original asphalt binder at 135°C using ASTM<br />
D 4402. The viscosity must not exceed 3 Pa.s to meet the requirements of MP1.<br />
7.6 After the RTFO test (T240) or TFO test (T179) is complete, determine the mass<br />
loss of the original asphalt binder. The mass loss must be _ 2.20 kPa to meet the requirements of<br />
MP1 (note 7).<br />
7.9 Age a sufficient quantity of RTFO or TFO residue in the PAV (PP1). Use an<br />
aging temperature of 90°C for binders having a high-temperature grading designation of PG<br />
229
46-x or PG 52-x, 100°C for binders having high-temperature grading designations of PG<br />
58-x and higher. A PAV temperature of 110°C is used in simulating desert environments.<br />
NOTE 8.--Two BBR beams requiring PAV material are required. In addition, four DT samples may also<br />
be needed requiring about 60 g of PAV-conditioned asphalt binder.<br />
7.10 Complete steps 7.1 through 7.9 during the first day of testing. This will allow<br />
further testing to begin on the second day, when the PAV procedure is complete.<br />
7.11 At the conclusion of the PAV procedure, carefully remove the residue from the<br />
vessel and combine individual pans of the same aged asphalt binder. Prepare two bending<br />
beam specimens according to TP1. Retain sufficient residue to prepare four direct tension<br />
specimens if required.<br />
7.12 Perform the DSR test (TP5) on the PAV residue at the test temperature<br />
specified in table 1 of MP1 indicated for the high-temperature and low-temperature grading<br />
designation of the binder being verified. For example, test a PG 64-40 asphalt binder at<br />
16°C. The value for G'sin 6 must not exceed 5000 kPa to meet the requirements of MP1<br />
(note 7).<br />
7.13 Test two BBR specimens according to TP1 at the test temperature specified in<br />
table 1 of MP1 indicated for the high temperature and low temperature grading designation<br />
of the binder being verified. For example, test a PG 58-28 asphalt binder at -18°C. The<br />
value of the slope in must be > 0.300 to meet the requirements of MP1. Certain asphalt<br />
binders may satisfy the BBR slope requirement at substantially lower temperatures than<br />
they satisfy the BBR stiffness requirement (note 7).<br />
7.14 Determine the extent of physical hardening, report the creep stiffness (S) and<br />
the slope (rn) of the log creep stiffness versus log time relationship measured at I hour<br />
(conducted above in section 7.13) and 24 hours. Prepare two BBR specimens of original<br />
asphalt binder. Condition and test the specimens at the test temperature, selected from table<br />
1 of MP1, appropriate for the performance grade of the asphalt binder. For example, if the<br />
binder grade being verified is a PG 64-34 asphalt binder, condition and test the BBR<br />
specimens at -24°C. Test one set after 1 hour of conditioning and the second set after 24<br />
hours of conditioning.<br />
7.15 If the creep stiffness is between 300.0 and 600.0 MPa and the slope m is _><br />
0.300 at the test temperature, it may be possible to satisfy the DT failure strain requirement<br />
in lieu of the creep stiffness requirement. Test four DT samples according to TP3 at the<br />
same test temperature used to test the BBR specimens. The failure strain must be >_1.0% to<br />
meet the requirements of MPI (note 7).<br />
230
8. REPORT<br />
8.1 If the grade of the asphalt binder tested is determined, report the results of all<br />
tests performed and the high temperature grading designation determined followed by the<br />
low temperature designation (for example: PG 52-34).<br />
8.2 If the grade of an asphalt binder is verified, report the results of all tests<br />
performed and if the binder meets the requirements of MP1.<br />
9. KEY WORDS<br />
Asphalt binder, performance<br />
grading.<br />
231
Standard Practice for<br />
Volumetric Analysis of Compacted Hot Mix Asphalt<br />
<strong>SHRP</strong> Designation: P-004<br />
NOTE1.--This practice is based upon chapter VI, Analysis of CompactedPaving Mixtures, of Asphalt<br />
Institute Manual MS-2.1<br />
NOTE2.--This practice is intendedto supplement the volumetric analysis and design procedures contained<br />
in the SUPERPAVE®Mix Design Manualfor New Constructionand Overlays.2<br />
1. SCOPE<br />
1.1 This practice provides procedures to accomplish the volumetric analysis of<br />
compacted hot mix asphalt (HMA) specimens.<br />
1.2 It presents methods for determining:<br />
• the volume percent of air voids (V_, also termed the air voids content);<br />
• the volume percent of voids in the mineral aggregate (VMA);<br />
• the voids filled with asphalt (VFA);<br />
• the effective volume of asphalt binder (Vbe); and<br />
• the effective asphalt content (Poe)<br />
of compacted HMA specimens.<br />
Values of these properties are calculated from the measured specific gravities of the asphalt<br />
binder, the coarse and fine aggregate, and the compacted HMA.<br />
1.3 This practice is applicable to specimens compacted in the laboratory or to<br />
specimens which are cut or cored from field pavements.<br />
1Manual MS-2, Mix Design Methods for Asphalt Concrete, 5th ed., The Asphalt Institute, Lexington, Ky.:<br />
1988.<br />
2R.J. Cominsky and E.T. Harrigan, SUPERPAVE®Mix Design Manual for New Construction and Overlays,<br />
<strong>SHRP</strong>, National Research Council, Washington, DC: 1993, Forthcoming.<br />
233
1.4 In order to attain adequate precision in the measured properties and calculated<br />
quantities, only compacted HMA specimens with a volume of 5.25 x 105 mm 3 or larger<br />
(equiyalent to a cylindrical specimen approximately 100 mm in diameter and 65 mm high)<br />
should be tested.<br />
1.5 The values stated in SI units are to be regarded as the standard.<br />
1.6 This standard may involve hazardous materials, operations and equipment. This<br />
standard does not purport to address all of the safety problems associated with its use. It is<br />
the responsibility of the user of this standard to establish appropriate safety and health<br />
practices and determine the applicability of regulatory limitations prior to use.<br />
2. APPLICABLE DOCUMENTS<br />
2.1 AASHTO Standards<br />
T84 Specific Gravity and Absorption of Fine Aggregate<br />
T85 Specific Gravity and Absorption of Coarse Aggregate<br />
T100 Specific Gravity of Soils<br />
TI64 Quantitative Extraction of Bitumen from Bituminous Paving Mixtures<br />
TI66 Bulk Specific Gravity of Compacted Bituminous Mixtures<br />
TI70 Recovery of Asphalt from Solution by Abson Method<br />
T209 Maximum Specific Gravity of Bituminous Paving Mixtures<br />
T228 Specific Gravity of Semi-Solid Bituminous Materials<br />
3. SIGNIFICANCE AND USE<br />
3.1 The proper design and field control of HMA volumetric parameters are critical to<br />
achieving satisfactory long-term pavement performance.<br />
4. DEFINITIONS<br />
NOTE 3.--Definitions<br />
4.1, 4.2, 4.3, 4.5 and 4.6 are excerpted from Asphalt Institute Manual MS-2.<br />
4.1 Air Voids (V_)--the total volume of the small pockets of air between the coated<br />
aggregate particles throughout a compacted paving mixture, expressed as percent of the bulk<br />
volume of the compacted paving mixture.<br />
4.2 Voids in the Mineral Aggregate (VMA)--the volume of intergranular void space<br />
between the aggregate particles of a compacted paving mixture that includes the air voids and<br />
the effective asphalt content, expressed as a percent of the total volume of the specimen.<br />
4.3 Effective Asphalt Content (Pb_)--the total asphalt content of a paving mixture less<br />
the portion of asphalt binder that is lost by absorption into the aggregate particles.<br />
234
4.4 Voids Filled with Asphalt (VFA)--the portion of the voids in the mineral<br />
aggregate that contain asphalt binder. This represents the volume of the effective asphalt<br />
content.<br />
4.5 Bulk Specific Gravity (G,o)- the ratio of the mass in air of a unit volume of a<br />
permeable material (including both permeable and impermeable voids normal to the material)<br />
at a stated temperature to the mass in air (of equal density) of an equal volume of gas-free<br />
distilled water at a stated temperature.<br />
4.6 Effective Specific Gravity (Gs_)--the ratio of the mass in air of a unit volume of a<br />
permeable material (excluding voids permeable to asphalt) at a stated temperature to the mass<br />
in air (of equal density) of an equal volume of gas-free distilled water at a stated<br />
temperature.<br />
4.7 Theoretical Maximum Specific Gravity (Gmm)- the ratio of the mass of a given<br />
volume of voidless (Va = 0) HMA at a stated temperature (usually 25 °C) to a mass of an<br />
equal volume of gas-free distilled water at the same temperature.1<br />
4.8 Volume of Absorbed Asphalt (Vb_)--the volume of asphalt binder in the HMA that<br />
has been absorbed into the pore structure of the aggregate, Vba is the volume of asphalt<br />
binder in the HMA for which the effective asphalt content cannot account.<br />
5. PROCEDURE<br />
NOTE4.--The accuracy of determinations of specific gravity for mix design is extremely important. Unless<br />
specific gravities are determined to three decimal places (four significant figures) an absolute error in the calculation<br />
of the air voids content of as much as 0.8% can occur (e.g., an actual value of 4.2% may be measured anywhere in<br />
the range of 3.4 to 5.0%). Therefore, balances of appropriate sensitivity must be used to measure the masses<br />
employed in the specific gravity determinations.<br />
5.1 Determine the percent of asphalt binder and aggregate by the total weight of the<br />
mixture (T164 and T170). Report as Pb and Ps, respectively.<br />
5.2 Separate the coarse (retained on the 4.75 mm sieve) and fine aggregate fractions<br />
from the mineral filler fraction (passing the 75/zm sieve). Calculate the percent of each<br />
fraction by the total weight of the aggregate and report as P1, P2 and P3, respectively.<br />
5.3 Measure the specific gravity of: the asphalt binder (T228); the coarse aggregate<br />
(T85); the fine aggregate (T84); and the mineral filler (T100). Report as G0, G1, G2 and G3,<br />
respectively.<br />
ICaution should be used when measuring the theoretical maximum specific gravity of HMA containing highly<br />
absorptive aggregates. Work conducted in <strong>SHRP</strong> Contract A-003B demonstrated that absorption may continue<br />
over a period of hours, and the value of G,.,. may change significantly until absorption is completed.<br />
235
5.4 Calculate the bulk specific gravity, Gsb, of the combined aggregate recovered<br />
from the HMA by the following equation:<br />
(e +e:e3)<br />
G,b-<br />
PI P2 P3<br />
5.5 Measure the theoretical maximum specific gravity of the compacted HMA (T209)<br />
and report as G_.<br />
5.6 Measure the bulk specific gravity of the compacted HMA (T166) and report as<br />
5.7 Calculate the effective specific gravity of the aggregate, Gse, by the following<br />
equation:<br />
(1oo-ep<br />
6 e-<br />
( I0___00 Pb)<br />
Gram G b<br />
5.8 Calculate the absorbed asphalt, Pba, as a percent by weight of the aggregate by<br />
the following equation:<br />
(G)(G_e-G,)×i00<br />
(6b6e)<br />
5.9 Calculatetheeffective asphaltcontent,PbeoftheHMA<br />
equation:<br />
by thefollowing<br />
P_ =Pb-[ (P_P_) ]<br />
100<br />
5.10 Calculate the percent voids in the mineral aggregate (VMA) by the following<br />
equation:<br />
VMA= 100-[ G_bPs]<br />
¢Jsb<br />
where Ps is the percent<br />
of aggregate by the total weight of the mixture.<br />
5.11 Calculate the percent air voids, Va, in the compacted HMA by the following<br />
equation:<br />
236
V - Gmm-G"b xlO0<br />
a G mm<br />
5.12 Calculate the percent of voids filled with asphalt binder (VFA) as a portion of<br />
the voids in the mineral aggregate by the following equation:<br />
VMA-V<br />
VFA -<br />
VMA<br />
a x 100<br />
6. REPORT<br />
6.1 Report specific gravity results to the nearest 0.001 and percent voids (VMA, Va<br />
and VFA) to the nearest 0.1.<br />
237
Standard Practice for<br />
Measurement of the Permanent Deformation and<br />
Fatigue Cracking Characteristics of<br />
Modified and Unmodified Hot Mix Asphalt<br />
<strong>SHRP</strong> Designation: P-0051<br />
1. _TRODUCTION<br />
1.1 This practice provides a laboratory guide for the analysis of the permanent<br />
deformation and fatigue cracking behavior of modified and unmodified (hot mix asphalt)<br />
(HMA) paving mixes with the SUPERPAVE ®shear test device.<br />
1.2 A sequence of tests conducted with the shear test device are required in both the<br />
SUPERPAVE ® level 2 and level 3 mix designs. These test results are used to calculate the<br />
pavement performance characteristics of a paving mix with the SUPERPAVE ® software.<br />
1.3 In addition to summarizing the test procedures, this practice provides guidance<br />
on the time requirements for completion of the level 2 and level 3 test sequences.<br />
1.4 The SUPERPAVE e shear test device is equipped with dual load actuators and is<br />
capable of simultaneously applying an axial and a shear load on the test specimen. It is also<br />
capable of applying a repetitive axial or shear load throughout a range of frequencies. This<br />
equipment is described in <strong>SHRP</strong> Standard Test Method M-003.<br />
1.5 The values stated in SI units are to be regarded as the standard.<br />
1.6 This standard may involve hazardous materials, operations and equipment. This<br />
standard does not purport to address all of the safety problems associated with its use. It is<br />
the responsibility of the user of this standard to establish appropriate safety and health<br />
practices and determine the applicability of regulatory limitations prior to use.<br />
2. SCOPE<br />
2.1 This is a practice for the performance-based testing of compacted specimens of<br />
modified or unmodified paving mix with the SUPERPAVE ® shear test device.<br />
_Thisstandard is based on <strong>SHRP</strong>Product 1017.<br />
239
2.2 This practice is applicable to specimens prepared in a laboratory mix design<br />
procedure or cored from a pavement for post-construction performance analysis.<br />
2.3 Compiete analysis of the test results from the SUPERPAVE ® shear test device<br />
requires the SUPERPAVE ®Specification, Mix Design and Support Program.<br />
3. REFERENCED DOCUMENTS<br />
3.1 The SUPERPAVE ° Mix Design Manual for New Construction and Overlays<br />
3.2 <strong>SHRP</strong> Test Method M-002, Preparation of Compacted Specimens of Modified<br />
and Unmodified Hot Mix Asphalt<br />
Compactor.<br />
Modified<br />
Test Specimens by Means of the <strong>SHRP</strong> Gyratory<br />
3.3 <strong>SHRP</strong> Test Method M-003, Determining the Shear and Stiffness Behavior of<br />
and Unmodified Hot Mix Asphalt with the SUPERPAVE ®Shear Test Device.<br />
3.4 AASHTO Test Method T166, Bulk Specific Gravity of Compacted Bituminous<br />
Mixtures.<br />
4. SUMMARY OF THE PRACTICE<br />
4.1 SUPERPAVE ®Level 2 Mix Design<br />
4.1.1 A sequence of three tests is performed with the shear test device in the level 2<br />
mix design. At each asphalt binder content, four specimens are tested at two different test<br />
temperatures. The level 2 test matrix is summarized in table 1.<br />
4.2 SUPERPAVE ®Level 3 MIX Design<br />
4.2.1 A sequence of five tests is performed with the shear test device in the level 3<br />
mix design. At each asphalt binder content, six specimens are tested at four different test<br />
temperatures. The level 3 test matrix is summarized in table 2.<br />
and 2.<br />
4.3 The following sequence of steps is common to each of the tests shown in tables 1<br />
4.3.1 Prepare test specimens. Saw specimen ends perpendicular to the longitudinal<br />
axis of the specimen; clean; measure dimensions; and determine specific gravity of each<br />
specimen.<br />
240
Table 1. Test Matrix for Level 2 Mix Design<br />
Test Method<br />
Number of Specimens at Test Temperature<br />
T_ (PD)<br />
T_ (FC)<br />
Repeated Shear at Constant Stress Ratio 2 --<br />
(Tertiary Creep)<br />
Simple Shear at Constant Height 2* 2*<br />
Frequency Sweep at Constant Height 2* 2*<br />
*The simple shear test at constant height and the frequency sweep at constant height are conducted on the<br />
same two specimens at both temperatures.<br />
Notes:<br />
Te_r(PD)is the calculated effective temperature for permanent deformation.<br />
T_(FC) is the calculated effective temperature for fatigue cracking. See chapter 4 of the<br />
SUPERPAVE® Mix Design Manual for New Construction and Overlays.<br />
Table 2. Test Matrix for Level 3 Mix Design<br />
Test Method<br />
Number of Specimens at Test Temperature<br />
4°C 20°C 40°C T_ (PD)<br />
Repeated Shear at Constant Stress Ratio -- -- -- 2<br />
(Tertiary Creep)<br />
Volumetric 2_ 2_ 2_ --<br />
Uniaxial Strain 2" 2" 2" --<br />
Simple Shear at Constant Height 2b 2b 2b --<br />
Frequency Sweep at Constant Height 2 8 2 b 2 b --<br />
"Tests performed on the same two specimens.<br />
bTests performed on the same two specimens.<br />
Notes:<br />
Teff(PD) is the calculated effective temperature for permanent deformation. See chapter 4 of the<br />
SUPERPAVE® Mix Design Manual for New Construction and Overlays'.<br />
4.3.2 Assemble the test assembly. As required, bond the platens to the test specimen;<br />
where required, surround the specimen with a membrane; and affix the linear variable<br />
differential transducers (LVDTs) to the specimen in the configuration required by the specific<br />
test.<br />
4.3,3 Load the completed test assembly into the shear test device.<br />
shear<br />
4.3.4 Conduct the test per <strong>SHRP</strong> M-003 and the manufacturer's instructions for the<br />
test device.<br />
241
4.3.5 At the compIetion of the test, remove the test assembly from the shear test<br />
device.<br />
4.3.6 Disassemble the test assembly. Discard or retain the test specimen and clean<br />
the end caps for reuse.<br />
5. GUIDELINES<br />
5.1 The following guidelines must be carefully followed before attempting to perform<br />
any of the tests described in this practice.<br />
5.1.1 Ensure that all load cells and LVDTs are accurately calibrated.<br />
5.1.2 Ensure that the correct channels and gains are entered into the system software<br />
before beginning any test.<br />
5.1.3 Clearly define the test conditions and enter them into the test device software.<br />
5.1.4 Allow sufficient time for the system to stabilize after the specimen is placed in<br />
the apparatus and before the test begins. This time will vary depending on the test<br />
temperature and the stiffness of the specimen. A typical stabilization time is 15 to 30<br />
minutes.<br />
5.1.5 Clearly identify the variables which are to be measured during the test.<br />
5.1.6 Turn on the hydraulic system 1 hour before starting the test to allow sufficient<br />
warm-up time.<br />
5.1.7 Condition all specimens at their initial test temperature for 2 hours before<br />
testing. For testing at 40°C or higher, the specimen should be placed in a 40°C (or<br />
designated temperature) oven for a period of at least 2 hours but not more than 4 hours.<br />
5.1.8 After the specimen is placed in the shear test device, apply a pre-load of 100 to<br />
150 N before the specimen is clamped in place.<br />
5.1.9 Perform a thorough check of the system for leakage before any test requiring<br />
specimen confinement with air pressure.<br />
5.1.10 Ensure that all measurement devices have reasonable sensitivities,<br />
commensurate with the load intensity and specimen deformation expected during each test.<br />
For example, the frequency sweep test requires a much more sensitive LVDT for horizontaI<br />
deformation measurement than for vertical deformation.<br />
242
6. SPECIMEN PREPARATION<br />
6.1 All test specimens must be 150 mm in diameter and 50.0 _.+2.5 mm high. Any<br />
appropriate procedure, such as AASHTO T166, Bulk Specific Gravity of Compacted<br />
Bituminous Mixtures, can be used to determine the specific gravity of the specimen. The<br />
dimensions of the specimens must be accurately measured and the top and bottom faces of<br />
the specimen must be smooth and parallel.<br />
6.2 Clean the platens and ensure that they are dust free.<br />
6.3 Place a pair of platens into the gluing jig provided with the shear test device,<br />
align them and clamp them into place.<br />
NOTE 1.--The<br />
platens are bonded to the specimen for all tests except the volumetric and uniaxial tests.<br />
6.4 Proportion and mix epoxy resin and hardener together in accordance with the<br />
manufacturer's instructions.<br />
NoTE 2.--Devcon 5-Minute Plastic Steel Epoxy Cement has been found to provide satisfactory performance<br />
for testing conducted at 20°C and higher. For low-temperature testing (typically at 4°C), Devcon Plastic Steel Epoxy<br />
Cement proved adequate.<br />
6.5 Ensure that the test specimen is dust flee. Apply a thin coating of epoxy cement<br />
(- 1.5 ram) to each end of the test specimen. Assure that the epoxy cement completely<br />
covers the specimen end and that it is of uniform thickness.<br />
6.6 Bond the specimen to the platens under a pressure of 30 to 40 kPa for the period<br />
of time recommended by the epoxy cement manufacturer.<br />
6.7 Remove the test assembly from the gluing jig. Allow the epoxy to cure for the<br />
time period recommended by the manufacturer.<br />
NoTE 3.--For Devcon 5-Minute Plastic Steel Epoxy, a curing time of 2 hours at room temperature is<br />
recommended.<br />
6.8 As required for specific tests, attach mounting screws for the horizontal LVDT(s)<br />
to the sides of the test specimen with epoxy cement (see notes 4 and 5).<br />
minutes.<br />
NoTE 4.--Gluing the specimen to the platens and attaching mounting screws for the LVDT takes about 15<br />
NoTE 5.--There are several alternative methods for mounting LVDTs. LVDTs measuring axial (vertical)<br />
deformation are generally attached directly to the platens. Similarly, LVDTs measuring shear (horizontal)<br />
deformation are typically mounted on blocks that are in turn attached to screws bonded to the specimen. They must<br />
measure the difference in horizontal displacement between two points on the specimen separated by at least 40 ram.<br />
Consult figure 5 in <strong>SHRP</strong> test method M-003 for specific LVDT mounting recommendations.<br />
243
7. TESTING OF SPECIMENS IN THE SUPERPAVE ® SHEAR TEST DEVICE<br />
7.1 Repeated Shear Test at Constant Stress Ratio (Tertiary Creep)<br />
7.1.1 Prepare the test specimen in accordance with section 6.<br />
7.1.2 Mount two LVDTs on the test assembly in such a manner that axial (vertical)<br />
and shear (horizontal) deformations can be measured dur_xlg the test with an accuracy and<br />
precision commensurate with the requirements of M-003.<br />
NOTE6.--This stress-controlledtest willusuallybe performedat an effectivetemperaturefor permanent<br />
deformationcalculatedfromweatherdatafor the siteof thepavingproject.Duringthe test, the ratioof the axial<br />
stressto the shearstressis keptconstantin orderto simulatethefieldstateof stressin a pavement.To accomplish<br />
this,the feedbackto thehorizontalloadzctuatorservovalveis fromthe magnitudeof the shearload.Thefeedbackto<br />
theverticalloadactuatorservovalveis fromthe magnitudeof the axialload.<br />
7.1.3 Place the specimen inside the shear test device and clamp it securely in place.<br />
7.1.4 Adjust the controls for the environmental chamber to the requisite test<br />
temperature and allow the chamber and the test assembly to stabilize at that temperature.<br />
7.1.5 Precondition the specimen by applying 100 cycles of synchronized haversine<br />
axial and shear load pulses with a peak magnitude of 7 kPa for shear stress. The axial stress<br />
for preconditioning should not exceed 7 kPa with the ratio axial to shear stress held constant<br />
at a value of 1.2 to 1.5. Each cycle is 0.7 second in duration, and consists of the application<br />
of a 0.1 second haversine load followed by a 0.6 second rest period.<br />
7.1.6 At the conclusion of the preconditioning, perform the repeated shear test for a<br />
duration of 5000 load cycles or until the permanent accumulated strain reaches a level of 5 %.<br />
A haversine shear load is applied with a maximum shear stress Ievel determined from<br />
table 3. The ratio of the haversine axial to shear load is maintained at a constant value<br />
between 1.2 and 1.5. Each test cycle is 0.7 second in duration, and consists of the<br />
application of a 0. i second haversine load followed by a 0.6 second rest period.<br />
Table 3. Maximum<br />
Shear Stress Levels<br />
im I_ i II I I<br />
AsphaltBinder Content1<br />
Base Condition2 Above Design At Design BelowDesign<br />
Weak Base 84 - 119 kPa 63 - 98 kPa 49 - 56 kPa<br />
Strong Base 98 - 175 kPa 84 - 105 kPa 56 - 91 kPa<br />
1Thedesign asphaltbinder content refers to the binder content selectedin the SUPERPAVE® level 1<br />
(volumetric)designmethod.<br />
2Aweak base is defined as an unboundgranularor crushedstone material,e.g., new construction;a strong<br />
base is definedas an existingasphalt concreteor portlandcementconcretepavement, cement-stabilizedor<br />
asphalt-stabilizedbase, or a strong crushed stone base material(with a resilient modulusof 560,000kPa or<br />
greater).<br />
II lit mill [ iNn i R<br />
244
Record axial deformation, shear deformation, axial load, and shear load during<br />
intervals shown in table 4 or at other appropriate intervals.<br />
7.--The test takes about 70 to 80 minutes to complete from the time the specimen is placed in the<br />
removed.<br />
Suggested Data Collection for the Repeated Shear Test at a Field State of Stress<br />
Collected During Cycles:<br />
1 through 10 1,747 through 1,750<br />
20 through 22 2,000 through 2,002<br />
30 through 32 2,247 through 2,250<br />
50 through 52 2,500 through 2,502<br />
80 through 82 2,748 through 2,750<br />
100 through 102 2,997 through 3,000<br />
200 through 202 3,200 through 3,202<br />
300 through 302 3,400 through 3,402<br />
400 through 402 3,600 through 3,602<br />
500 through 502 3,800 through 3,802<br />
600 through 602 3,997 through 4,000<br />
800 through 802 4,200 through 4,202<br />
1,000 through 1,002 4,500 through 4,502<br />
1,247 through 1,250 4,998 through 5,000<br />
1,500 through 1,502<br />
duration of each cycle is 0.7 second.<br />
collection rate of 60 data points per second is satisfactory.<br />
Volumetric Test<br />
Place the specimen (prepared in accordance with sections 6.1 and 6.2) between<br />
bottom platens.<br />
Surround the specimen with a membrane,<br />
open at both ends and free of any defects.<br />
150 mm in diameter and 0.6 mm<br />
Fix the membrane tightly to the platens with rubber O-rings.<br />
Mount a radial LVDT around the circumference of the specimen to measure its<br />
deformation. Then mount LVDTs on both sides of the specimen to measure axial<br />
from platen to platen.<br />
245
7.2.5 Since the specimen will be subjected to confining pressure with compressed air<br />
during the test, confirm that the system is not leaking before starting the test. Thoroughly<br />
check the membrane and all connecting hoses and fittings, and replace or tighten as<br />
necessary.<br />
NOTE8.--Vacuumcanbe usedto checkfor defectiveconnectionsor a faultymembranewhichmaycause<br />
Ieakage.Twohosesconnectthe platensto the outsideof the confiningcellandto the atmosphere.Thesehoses<br />
preventthe buildupof air pressurebetweenthe specimenandthe membrane,andserveto warnof anyleaksin the<br />
membraneor the sealsbetweenthe membraneandtheplatens.<br />
7.2.6 Place the completed specimen test assembly into the testing cell in the shear<br />
test device. Confn'm that the specimen is in the center of the cell and not in contact with the<br />
surrounding walls, and that the radial LVDT can move freely around the specimen without<br />
any interference from other objects.<br />
7.2.7 Lower the confining cell and lock in place. Bring the specimen assembly to the<br />
required test temperature and allow sufficient time for the temperature to stabilize.<br />
7.2.8 Open the air pressure valve to begin the test. Precondition the specimen by<br />
rapidly applying, then removing hydrostatic pressure. Ramp the pressure to 70 kPa in one<br />
second and immediately reduce it to 7 kPa.<br />
7.2.9 Conduct the volurnetric test by increasing the hydrostatic pressure at a rate of<br />
70 kPa/s to: 550 kPa at 40°C, 690 kPa at 20°C, or 830 kPa at 4°C. Maintain the pressure at<br />
that Ievel for 10 seconds and then reduce it to 7 kPa at a rate of 25 kPa/s. Hold the specimen<br />
at this pressure<br />
for an additional 30 seconds.<br />
7.2.10 Record the axial deformation on both sides of the specimen, the radial<br />
deformation, and the hydrostatic pressure at a rate of about 10 data points per second.<br />
NOTE9.--The volumetrictesttakesabout30 minutesto complete.Thisincludesset-up,placingof the<br />
specimenin the cell, runningthe test, andremovingthe specimenfromthe apparatus.<br />
7.3 Uniaxial Strain Test<br />
7.3.1 Place the specimen (prepared in accordance with sections 6.1 and 6.2) between<br />
the top and bottom platens.<br />
thick,<br />
7.3.2 Surround the specimen with a membrane, 150 mm in diameter and 0.6 mm<br />
that is open at both ends and free of any defects.<br />
7.3.3 Fix the membrane tightly to the platens with rubber O-rings.<br />
7.3.4 Mount a radial LVDT around the circumference of the specimen to measure its<br />
radial deformation. Then mount LVDTs on both sides of the specimen to measure axial<br />
deformation<br />
from platen to platen.<br />
246
7.3.5 Since the specimen will be subjected to confining pressure with compressed air<br />
during the test, confirm that the system is not leaking before starting the test. Thoroughly<br />
check the membrane and all connecting hoses and fittings, and replace or tighten as<br />
necessary (note 8).<br />
7.3.6 Place the completed specimen test assembly into the testing cell in the shear<br />
test device with a 75 mm circular loading unit placed between the vertical (axial) load cell<br />
and the top platen to provide a uniform stress distribution. Confirm that the specimen is in<br />
the center of the cell and not in contact with the surrounding walls, and that the radial LVDT<br />
can move freely around the specimen without any interference from other objects.<br />
7.3.7 Lower the confining cell and lock in place. Bring the specimen assembly to the<br />
required test temperature and allow sufficient time to stabilize the temperature.<br />
NOTE 10.--During the test the confining pressure is adjusted by closed loop feedback control from the<br />
radial LVDT to maintain the circumference of the specimen at a constant value and prevent radial deformation of the<br />
specimen during the test.<br />
7.3.8 Open the air pressure valve to begin the test. Precondition the specimen by<br />
applying an axial load which is induced at the rate of 70 kPa/s for one second and<br />
immediately reduced to 7 kPa.<br />
7.3.9 Conduct the uniaxial strain test by increasing the axial stress at a rate of 70<br />
kPa/s to: 345 kPa at 40°C, 550 kPa at 20°C, or 655 kPa at 4°C. Maintain the stress at that<br />
level for 10 seconds and then reduce it to 7 kPa at a rate of 25 kPa/s. Hold for an additional<br />
30 seconds at this stress level.<br />
7.3.10 Record the axial deformation on both sides of the specimen, the radial<br />
deformation, the axial load, and the confining pressure at appropriate intervals and at a rate<br />
of about 10 data points per second.<br />
NOTE 11.--The uniaxial strain test takes about 30 minutes to complete. This includes setup, placing of the<br />
specimen in the cell, running the test, and removing the specimen from the apparatus.<br />
7.4 Simple Shear Test at Constant Height<br />
7.4.1 Prepare the test specimen in accordance with section 6.<br />
7.4.2 Mount two LVDTs on the test assembly in such a manner that axial (vertical)<br />
and shear (horizontal) deformations can be measured during the test with an accuracy and<br />
precision commensurate with the requirements in Test Method M-003.<br />
NOTE 12.--This is a stress-controlled test. During the test, the height of the specimen is kept constant. To<br />
accomplish this, the vertical load actuator is controlled by feedback from the vertical (axial) LVDT. The feedback to<br />
the horizontal (shear) load actuator is from the magnitude of the shear load.<br />
7.4.3 Place the specimen inside the shear test device and clamp it securely in place.<br />
247
7.4.4 Adjust the controls for the environmental chamber to the requisite test<br />
temperature and allow the chamber and the test assembly to stabilize at that temperature.<br />
7.4.5 Precondition the specimen for 100 cycles with a shear stress of 7 kPa. Each<br />
cycle is 0.7 second in duration, and consists of the application, of a 0.1 second haversine load<br />
followed by a 0.6 second rest period.<br />
7.4.6 At the conclusion of the preconditioning, perform the simple shear test by<br />
increasing the shear stress at a rate of 70 kPa/s to: 345 kPa at 40°C or T_ff(PD), 105 kPa at<br />
20°C or Teff(FC), or 35 kPa at 4°C. Maintain the stress at that level for 10 seconds and then<br />
reduce it to 0 kPa at a rate of 25 kPa/s. Continue the test for an additional 10 seconds at a<br />
stress level of 0 kPa.<br />
7.4.7 Record axial deformation, shear deformation, axial load, and shear load at a<br />
rate of about 10 data points per second.<br />
NOTE 13.--The test takes about 20 to 30 minutes to complete from the time the specimen is placed in the<br />
apparatus until it is removed.<br />
7.5 Frequency Sweep Test at Constant Height<br />
7.5.1 Prepare the test specimen in accordance with section 6.<br />
7.5.2 Mount two LVDTs on the test assembly in such a manner that axial (vertical)<br />
and shear (horizontal) deformations can be measured during the test with an accuracy and<br />
precision commensurate with the requirements in M-003 (note 5).<br />
NOTE 14.--This is a strain-controlled test. The maximum strain is limited to 1 x 10 -4 mm]mm. During the<br />
test, the height of the specimen is kept constant. To accomplish this, the vertical load actuator is controlled by<br />
feedback from the vertical (axial) LVDT. The feedback to the horizontal (shear) load actuator is from the LVDT<br />
measuring the horizontal (shear) deformation.<br />
7.5.3 Place the specimen inside the shear test device and clamp it securely in place.<br />
7.5.4 Adjust the controls for the environmental chamber to the requisite test<br />
temperature and allow the chamber and the test assembly to stabilize at that temperature.<br />
7.5.5 Precondition the specimen by applying a sinusoidal shear (horizontal) strain of<br />
approximately 1 x 10 -4 ram/ram at a frequency of 10 Hz for 100 cycles.<br />
7.5.6 At the conclusion of the preconditioning, perform the frequency sweep test in<br />
which 100 cycles of 1 x 10 -4 mm]mm sinusoidal shear (horizontal) strain is applied at the<br />
each of the following frequencies in descending order: 10, 5, 2, 1, 0.5, 0.2, 0.1, 0.05, and<br />
0.02 Hz. Repeat the test on each specimen at three different temperatures, typically 4, 20<br />
ar:d 40°C, starting at the lowest temperature.<br />
7.5.7 Record axial deformation, shear deformation, axial load, and shear load at a<br />
rate of about 50 data points per load cycle.<br />
248
NOTE 15.--At each temperature, the test takes about 45 to 55 minutes per specimen to complete from the<br />
time the specimen is placed in the apparatus until it is removed.<br />
8. CLEANUP<br />
8.1 At the conclusion of each test requiring specimens bonded to the platens, place<br />
the specimen-platen assembly in a 135°C oven for 15 to 20 minutes to disbond specimen and<br />
epoxy from the platens. Clean the platens with acetone (or other suitable solvent<br />
recommended by the manufacturer of the epoxy cement) in an operating fume hood and dry<br />
with compressed air before use with a new specimen.<br />
9. TESTING TIME AND SCHEDULE<br />
9.1 The time required to complete the test sequence needed for a level 2 or level 3<br />
mix design will depend upon a number of factors: the speed with which the test temperature<br />
can be changed and stabilized in the SUPERPAVE ® shear test device; work-shift scheduling;<br />
the skill and number of technicians; and the technicians' familiarity with the shear test device<br />
and its ancillary equipment.<br />
9.2 Table 5 is a guide to the time required to accomplish different segments of the<br />
procedure for one trial paving mix (one asphalt binder content) under normal laboratory<br />
conditions in a level 3 mix design.<br />
Table 5. Time Estimate<br />
for Level 3 Mix Design<br />
Procedure or Test Method Number of Tests per Number of Time 0trs)<br />
Temperature<br />
Temperatures<br />
Compaction and Preparation of Eight - _ 6<br />
Specimens<br />
Bonding to Platens and Mounting of - _ 1<br />
LVDT Screws<br />
Repetitive Shear at Constant Stress 2 1 3<br />
Ratio<br />
Frequency Sweep 2 3 4<br />
Simple Shear 2 3 2<br />
Volumetric 2 3 2.5<br />
Uniaxial Strain 2 3 2.5<br />
Data Preparation - - 2<br />
Temperature Changes - - 6<br />
Total hours: 27<br />
249
9.3 The length of the total test period is also affected by the initial time required to<br />
set up the systems and calibrate the measurement devices. A more efficient testing schedule<br />
is achievable if several paving mixes are tested simultaneously; the average time spent per<br />
paving mix will be less than, for instance, the time needed when only one paving mix is<br />
being tested.<br />
9.4 Table 6 presents an estimated testing schedule for a complete levet 3 mix design,<br />
involving three asphalt binder contents and the testing of 24 specimens.<br />
Table 6. Testing Schedule for a Level 3 Mix Design<br />
1 i i Ill i i<br />
Activity<br />
Time Period<br />
• Compact specimens and cut parallel faces. Days 1 through 4<br />
• Measure specimen dimensions arm specific<br />
gravities.<br />
• Set up equipment and calibrate measurement<br />
devices.<br />
• Bond specimens to platens and mount LVDT<br />
screws.<br />
• Run repeated shear test (constant stress ratio) at Day 5<br />
Te_(eD)<br />
• Run frequency sweep and simple shear tests at am of Day 6<br />
4°C.<br />
• Run frequency sweep and simple shear tests at pm of Day 6<br />
20°C.<br />
* Run frequency sweep and simple shear tests at am of Day 7<br />
40°C.<br />
• Run volumetric and uniaxial strain tests at 4°C. pm of Day 7 through<br />
am of Day 8<br />
• Run volumetric and uniaxial strain tests at 20°C. pm of Day 8<br />
• Run volumetric and uniaxial strain tests at 40°C. am of Day 9<br />
• Preparation of data flies for analys_s in pm of Day 9<br />
SUPERPAVE ® software.<br />
ii I I I I<br />
9.5 A level 2 mix design requires significantly fewer specimens and tests, and<br />
consequently, substantially less testing time. Table 7 is a guide to the time required to<br />
accomplish different segments of the procedure for one trial paving mix (one asphalt binder<br />
content) under normal laboratory conditions in a level 2 mix design.<br />
9.6 Table 8 presents an estimated testing schedule for a complete level 2 mix design,<br />
involving three asphalt binder contents and the testing of 18 specimens.<br />
250
Table 7. Time Estimate for Level 2 Mix Design<br />
Procedure or Test Method Number of Tests Number of Time Oars)<br />
per Temperature Temperatures<br />
Compaction and Preparation of Six - - 4<br />
Specimens<br />
Bonding to Platens and Mounting of - - 1<br />
LVDT Screws<br />
Repetitive Shear at Constant Stress 2 1 3<br />
Ratio<br />
Frequency Sweep 2 1 2<br />
Simple Shear 2 1 1<br />
Data Preparation - - 2<br />
Temperature Changes - - 2<br />
Total Hours: 15<br />
Table 8. Testing Schedule for a Level 2 Mix Design<br />
Activity<br />
Time Period<br />
• Compact specimens and cut parallel faces. Days 1 through 3<br />
• Measure specimen dimensions and specific<br />
gravities.<br />
• Set up equipment and calibrate measurement<br />
devices.<br />
• Bond specimens to platens and mount LVDT<br />
screws.<br />
• Run repeated shear test (constant stress ratio) at Day 4<br />
T_u(PD).<br />
• Run frequency sweep and simple shear tests at am of Day 5<br />
To_(FC).<br />
• Run frequency sweep and simple shear tests at pm of Day 5<br />
T_(PD).<br />
• Preparation of data files for analysis in am of Day 6<br />
SUPERPAVE ® software.<br />
10. REPORT<br />
10.1 Report all test results as computer files compatible with and readable by the<br />
SUPERPAVE ® Specification, Mix Design and Support Program.<br />
251
ANNEX<br />
AL OPTIONAL RAPID METHOD FOR ESTIMATION OF RUT DEPTH USING<br />
THE REPEATED SHEAR TEST AT CONSTANT HEIGHT<br />
A1.1 Scope<br />
AI.I.1 Tl_2smethod permits a rapid estimation of rut depth for any mix design over<br />
the service life of a pavement (expressed as total design ESALs).<br />
NOTEA1.1.--This method is based upon the research results presented in the Asphalt-Aggregate Mix<br />
Design Using the Constant Height Repetitive Simple Shear Test prepared by Jorge B. Sousa of the University of<br />
California at Berkeley for the 1994 Annual Meeting of the Transportation Research Board.<br />
A1.2 Procedure for Estimation of Rut Depth<br />
A1.2.1 Estimate the total number of design ESALs, ESAL, expected on the pavement<br />
during its effective service life.<br />
A1.2.2 Using the SUPERPAVE ®Specification, Mix Design and Support Program<br />
software, estimate Tn_x(d), tiae maximum pavement design temperature expected at depth d in<br />
the pavement from historical air temperature data. This is the maximum average pavement<br />
temperature during the hottest 7-day period in an average year.<br />
A1.2.3 Calculate the number of loading cycles in the repeated shear test at constant<br />
height that are equivalent to the total design ESALs from the equation:<br />
Iog(cycles) = - 4.36 + [1.24 x log(ESAL]<br />
A1.2.4 Conduct the repeated shear test at constant height at T,,_(d) according to the<br />
procedure in section A1.3 and determine the maximum permanent shear strain at the number<br />
of load cycles determined in A1.2.3.<br />
A1.2.5 Estimate the rut depth in mm expected at the total number of design ESALs<br />
from the equation:<br />
Rut Depth(mm) =279.4 × [Maximum Permanent<br />
Shear Strain]<br />
A1.3 Repeated Shear Test at Constant Height<br />
A1.3.1 Prepare the test specimen in accordance with section 6.<br />
A1.3.2 Mount two LVDTs on the test assembly in such a manner that axial (vertical)<br />
and shear (horizontal) deformations can be measured during the test with an accuracy and<br />
precision commensurate with the requirements in Test Method M-003 (see note 5).<br />
252
NOTEA1.2.--This stress-controlled test will usually be performed at a maximum pavement design<br />
temperature calculated at depth d in the pavement from weather data for the site of the paving project. During the<br />
test, the height of the specimen is kept constant. To accomplish this, the vertical load actuator is controlled by<br />
feedback from the vertical (axial) LVDT. The feedback to the horizontal (shear) load actuator is from the magnitude<br />
of the shear load.<br />
A1.3.3<br />
Place the specimen inside the shear test device and clamp it securely in place.<br />
A1.3.4 Adjust the controls for the environmental chamber to the requisite test<br />
temperature and allow the chamber and the test assembly to stabilize at that temperature.<br />
A1.3.5 Precondition the specimen for 100 cycles with a shear stress of 7 kPa. Each<br />
cycle is 0.7 second in duration, and consists of the application of a 0.1 second haversine load<br />
followed by a 0.6 second rest period.<br />
A1.3.6 At the conclusion of the preconditioning, perform the repeated shear test for<br />
a duration of 5000 load cycles or until the permanent accumulated strain reaches a level of<br />
5 %. Apply a haversine shear load with a maximum shear stress level of 48 kPa. The axial<br />
load is varied automatically during each cycle to maintain the specimen at constant height.<br />
Each test cycle is 0.7 second in duration, and consists of the application of a 0.1 second<br />
haversine load followed by a 0.6 second rest period.<br />
A1.3.7 Record axial deformation, shear deformation, axial load, and shear load<br />
during the test at the intervals shown in table 4 or at other appropriate intervals.<br />
NOTEA1.3.--The test takes about 60 to 70 minutes to complete from the time the specimen is placed in the<br />
apparatus until it is removed.<br />
253